Thomas Carlyle's Sartor Resartus is like Thus Spake Zarathustra, but with a sense of humor.
Sartor Resartus is the effort of an imaginary English translator/editor to describe the life and opinions of a solitary, mysterious German writer named Diogenes Teufelsdröckh ("God-born Devil-dung"), professor of Things-in-General at the University of Weissnichtwo ("don't know where"), residing in his rooms on the Wahngasse ("Madness Street"), and author of the treatise Clothes: Their Origin and Influence. The book, containing pompous "translations" and summaries of Teufelsdröckh's autobiographical scribblings--literally scraps of paper sorted in bags by symbols of the zodiac--and of his magnum opus, is in part a parody of German philosophy in the first half of the 19th century, but also a vehicle for Carlye to expound some of his own opinions.
Carlyle himself seems to have been a proto-existentialist, a branch of philosophy generally associated not with him but with the later Nietzsche. Both the men and their works share important similarities. Both Carlyle and Nietzsche grew up in sternly religious families and were expected to become ministers, but both rejected the faith of their youth. And yet the writings of both men retain a strongly religious feeling. The most striking evidence is that both men make use of hermits to stand for wisdom-seekers in their philosophy. Teufelsdröckh, after being rejected by his true love Blumine roams the world like the Wandering Jew, pursued by his shadow. Zarathustra, on the other hand, remains in solitude on a mountaintop before deciding to re-enter the world. (Interestingly, Nietzsche also used the figure of the wanderer and his shadow, as witness his dialogue Der Wanderer und sein Schatten.)
The most important similarity between Sartor Resartus and Thus Spake Zarathustra, though, is the message at the heart of their existentialist philosophy: each individual must need for affirm the goodness of the world, say yes to it. This is a message that can and should be taken up by Christians, albeit with some modifications, as it was by Josef Pieper in Zustimmung zur Welt. 
In the biographical section of Sartor Resartus, Carlyle sets out three states of soul through which Teufelsdröckh passes: The Everlasting No, the Center of Indifference, and the Everlasting Yea. Only in the Everlasting Yea, when he affirms the goodness of the world, does he attain spiritual perfection. The "everlasting No" is not simply rejection of the world, but is also profound defiance. It can best be given in Teufelsdröckh's own words from his conversation with himself during a quasi-mystical experience on the Rue Saint-Thomas de l'Enfer in Paris, when he was sunk in misery after Blumine forsook him to marry a mutual friend:
Despicable biped! what is the sum-total of the worst that lies before thee? Death? Well, Death; and say the pangs of Tophet too, and all that the Devil and Man may, will or can do again against thee! Hast thou not a heart: canst thou not suffer whatsoever it be; and, as a Child of Freedom, though outcast, trample Tophet itself under thy feet, while it consumes thee? Let it come, then; I will meet it and defy it!"
In the Everlasting No, the individual is totally alienated and is thrown back upon his own freedom. In the midst of his despair, he decides to face death with nothing but his own will power to aid him.
The Center of Indifference marks an intermediate stage through which souls pass from the everlasting Yea to the everlasting No. The soul is still sick, but is also recovering from the defiant despair by which he has been afflicted up until now; the worst symptoms are now in remission. Or, as Teufelsdröckh's English editor describes it, in terms of demonic possession:
We should rather say that Legion, or the Satanic School, was now pretty well extirpated and cast out [of Teufelsdröckh], but next to nothing introduced in its room; whereby the heart remains, for the while, in a quiet but no comfortable state.
Only the everlasting Yea marks the decisive break with despair and defiance. Teufelsdröckh's account of his conversion bears quoting in full in his hyperbolic, exaggeratedly Germanic and professorial style:
Es leuchtet mir ein, I see a glimpse of it...there is in man a Higher than Love of Happiness; he can do without Happiness, and instead thereof find Blessedness! Was it not to preach-forth this same Higher that sages and martyrs, the Poet and the Priest, in all times, ahve spoken and suffered; bearing testimony, though life and through death, of the Godlike that is in Man, and how in the Godlike only has he Strength and Freedom? Which God-inspired Doctrine art thou also honoured to be taught; O Heavens! and broken with manifold merciful Afflictions, even till thou become contrite, and learn it! O, thank thy Destiny for these; thankfully bear what yet remain: thou hadst need of them; the Self in thee needed to be annihilated. By benignant fever-paroxysms is Life rooting out the deep-seated chronic Disease, and triumphs over Death. On the roaring billows of Time, thou art not engulfed, but borne aloft into the azure of Eternity. Love not Pleasure; love God. This is the Everlasting Yea, wherein all contradiction is solved: wherein whoso walks and works, it is well with him.What is noteworthy about this passage is that Teufelsdröckh preaches something higher than happiness, for happiness would be too selfish. Instead, he preaches blessedness in the form of annihilation of the self. Love of God, and affirmation of the world, are one and the same thing, but they entail annihilation of the self. The result of this affirmation is to be "borne aloft into the azure of Eternity." The sense of disappearing into God and nature--if there is even a distinction in Carlyle's mind--is palpable here.
However, even though all three writers believe that affirmation of the world is necessary, they all differ from each in exactly how they affirm the goodness of the world. Nietzsche sings the glory of affirmation in poems and rhapsodic prose in Zarathustra, and even states in one of his posthumously published aphorisms: "To have joy in anything, one must approve everything." But in his post-Zarathustra writings it is not quite clear whether he actually can affirm the goodness of the world. He writes his autobiography and calls himself the "Antichrist." Nietzsche may claim that he just wants to affirm the world, but it seems that he is really more of a rebel, defiant in his despair, and angry at the Christian God. As Romano Guardini says of Nietzsche, his portrayal of the perfect man as a "man who can dance" on the surface of nothingness is a Sehnsuchtsbild, a projection of his longing to attain a freedom of spirit and affirmation of the world that he could never actually achieve himself.  The man who wanted to overcome himself tragically could not overcome the Everlasting No.
Carlyle reaches a more authentic affirmation than Nietzsche, but he is so full of irony that it can sometimes be hard to tell whether he secretly harbors reservations. On the positive side, his humor can be seen as a sign that he has come to accept the world. He can call the young Teufelsdröckh by the diminutive "Gneschen"! Nietzsche never could have written about a spiritual hero and called him by the nickname "Thustralein." Carlyle's English "editor" can also point out flaws in his author's style and organization, and even criticize some of his opinions. The sometimes flippant humor shows that he is not in continuous agony, like Nietzsche.
Moreover, Carlyle recognizes that our very existence is a miracle. This is one of Carlyle's core beliefs, and one which forms the basis of his affirmation of the world. He repeats this belief in clearer form in his essay on Odin in On Heroes, Hero-Worship, and the Heroic in History: "This world, after all our science and sciences, is still a miracle; wonderful, inscrutable, magical and more, to whosoever will think it." (Carlyle also holds that wonder at the divinity of nature is the chief characteristic of paganism--strikingly similar to G.K. Chesteron's views.)
On the other hand, Carlyle's irony may signal that he still feels some detachment from the world. One wonders at times whether the irony really indicates that Carlyle cannot but view the wanderings and despair of Teufelsdröckh with quiet ridicule. He may still be stuck in the Center of Indifference.
Furthermore, Carlyle was strongly influenced by German Idealism and its undercurrent of pantheism. While he was not a full-pledged pantheist, there are times when Carlyle blurs the distinction between God and nature. Moreover, in the tradition of earlier mystics, Carlyle also views happiness as an annihilation of self. In a later essay on Mohammad (also in On Heroes), he states: "Islam means in its way Denial of Self, Annihilation of Self. This is yet the highest Wisdom that Heaven has revealed to our Earth." This equation of denial of self--what Christ has called all his followers to practice--with annihilation of self--a false form of immanentism rampant in German Idealism--sets up a contradictory relationship to the world. If one hopes for one's self to be annihilated, how can one also affirm the goodness of the world? The two are not compatible--so long as one wishes to remain part of this world. An orthodox Christian, on the other hand, denies himself so that he can follow Christ more obediently and ascend to the source of this beautiful world with Him, not to be annihilated, even in the beatific vision. 
Only Pieper, with his characteristic serenity--remarkable for a man who lived through some of the most turbulent times in a country at the center of the last century's upheavals--seems to have actually assented to the world and reached the truly Everlasting Yea. And it is obvious from the types of books he wrote: a Theory of Festivity as well as Happiness and Contemplation; he wrote about affirming the goodness of the world without the rancor of Nietzsche or the irony of Carlyle. In a world turned upside down and full of fashionable sophists like Sartre who called being born absurd, he undertook the difficult task of explaining why the world was good, and why we should say "yes" to it. What made it possible for Pieper to attain the everlasting Yea was his belief in a transcendent God who does not demand self-annihilation as a prerequisite to happiness (or blessedness), as opposed to the quasi-Spinozan God of Teufelsdröckh and Carlyle. For Pieper, who saw himself as developing the key concept of Kreatürlichkeit ("creatureliness") he found in St. Thomas Aquinas, existence was even more of a miracle than for Carlyle--the free act of a Creator who was under no compulsion to make the world. Only with his belief in a transcendent God who created and redeemed the world could Pieper say, "Lord, it is good that I am here!"
The Everlasting Yea, in its sublimest form, is a fundamental affirmation of the goodness of the world and of its Creator. And for each of these authors, the Everlasting Yea is the source of any spiritual serenity they experienced.
 Pieper's book is available in English translation as In Tune with the World, but I hesitate to call it by that title because it is a mistranslation of the German: Zustimmung means affirmation, assent, agreement, or approval; it implies an active decision to say "yes" to something, not a passive surrender.
 Romano Guardini, Vom Sinn der Schwermut (Mainz: Matthias-Grünewald-Verlag, 2003), p. 24.
 Readers interested on the question of pantheism should consult Thomas Molnar, God and the Knowledge of Reality (New York: Basic Books, 1973).