Nietzsche and his illness
Two Happy Ones.—Certainly this man, notwithstanding his youth, understands the improvisation of life, and astonishes even the acutest observers. For it seems that he never makes a mistake, although he constantly plays the most hazardous games. One is reminded of the improvising masters of the musical art, to whom even the listeners would fain ascribe a divine infallibility of the hand, notwithstanding that they now and then make a mistake, as every mortal is liable to do. But they are skilled and inventive, and always ready in a moment to arrange into the structure of the score the most accidental tone (where the jerk of a finger or a humour brings it about), and to animate the accident with a fine meaning and a soul.
—Here is quite a different man: everything that he intends and plans fails with him in the long run. That on which he has now and again set his heart has already brought him several times to the abyss, and to the very verge of ruin; and if he has as yet got out of the scrape, it certainly has not been merely with a "black eye." Do you think he is unhappy over it? He resolved long ago not to regard his own wishes and plans as of so much importance. "If this does not succeed with me,"—he says to himself, "perhaps that will succeed; and on the whole I do not know but that I am under more obligation to thank my failures than any of my successes. Am I made to be headstrong, and to wear the bull's horns? That which constitutes the worth and the sum of life for me, lies somewhere else; I know more of life, because I have been so often on the point of losing it; and just on that account I have more of life than any of you!" - Aphorism 303, The Gay Science
Nietzsche's philosophy has been greatly influenced by his chronic illness. Plagued by migraines since childhood -migraines that would become so severe that he would lose the ability to write, forcing him to resort to a rudimentary writing machine and also to the aphoristic style- Nietzche discovered in himself the will to be a "yes-sayer" and embrace his fate. He used to find peace during his long walks in the Swiss mountains, in Genoa, and he clearly felt free, in spite of the illness that eventually impaired him and swiftly drove him to his death bed, at 55. And I cannot find something more powerful than his philosophy, one of optimism and love for life, one embracing great themes of freedom and travel, knowing the physical pain he was going through at all times.
In his preface to The Gay Science, he explains the effects that sickness and covalescence has on his writing and state of mind.
"After such self-questioning, self-temptation, one acquires a subtler eye for all philosophizing to date; one can infer better than before the involuntary detours, side lanes, resting places, and sunny places of thought to which suffering thinkers are led and misled on account of their suffering: for now one knows whether the sick body and its neceds unconsciously urge, push, and lure the spirittoward the sun, stillness, mildness, patience, medicine, balm in some sense."
Pretty much the entirety of his philosophical work has been shaped by his condition. Amor Fati was originally a concept that belonged to the Stoics. They resigned themselves to simply accept their fate as we lack control over it. Nietzsche's version is different. It is not a rationalist view but it entails loving your fate. Amor fati, accepts life, and by extension fate, in all its variations. You are not entitled to being in or receiving or perceiving the shallow or deep pleasurable or comfortable aspects of it alone. Nietzsche never verbatim said that all the weak must perish or that there is meaning in suffering. He is a lot more of an observer as opposed to a crusader than people give him credit for. What Nietzsche does argue however is that we should accept the cruelty of life in equal measure to its pleasure.
In The Gay Science he goes into this more in depth, in his suggestively named aphorism "Wisdom in pain"
"Wisdom in pain- In pain there is as much wisdom as in pleasure: like the latter it is one of the best self-preservatives of a species. Were it not so, pain would long ago have been done away with; that it is hurtful is no argument against it, for to be hurtful is its very essence. In pain I hear the commanding call of the ship's captain: "Take in sail!" "Man," the bold seafarer, must have learned to set his sails in a thousand different ways, otherwise he could not have sailed long, for the ocean would soon have swallowed him up. We must also know how to live with reduced energy: as soon as pain gives its precautionary signal, it is time to reduce the speed—some great danger, some storm, is approaching, and we do well to "catch" as little wind as possible.—It is true that there are men who, on the approach of severe pain, hear the very opposite call of command, and never appear more proud, more martial, or more happy, than when the storm is brewing; indeed, pain itself provides them with their supreme moments! These are the heroic men, the great pain-bringers of mankind: those few and rare ones who need just the same apology as pain generally,—and verily, it should not be denied them! They are forces of the greatest importance for preserving and advancing the species, were it only because they are opposed to smug ease, and do not conceal their disgust at this kind of happiness." - Aphorism 318, Book Four
As long as there is something which we have to experience, we might as well see the value in having experienced it.