Nietzsches poor health is often observed as weakness, mostly by people whom did not get deep into the subject, which devaluets the writings and doing of that man. But he was aware himself that his philosophy is not a philosophy of joy, of sanity and health but a philosophy of pain, struggle and fighting for life.
The illness whis had befallen Friedrich Nietzsche is speculated to have been some degenration of the neuralsystem, his father before has become suddenly very ill and died with the diagnosis of "Gehirnerweichung" which was a common description for a degenerative illness of the brain which leads to death.Claus Ludwig Nietzsche died at the age of 35, leaving his family behind. In the same age of 35, Friedrich Nietzsche, now professor in the faculty of the university of Basel hat to lay down his professorship for health issues, including painful headaches, progressing blindness and a in general poor health, which get more worse every day until his mental breakdown 10 years later at the age of 45.
The ten years in between as a free philosopher was a permanent struggle for painfree moments, for sleep and against the loneliness. Step by step, his friends and collagues went away from him, not able to understand his workings and thoughts. The women also rejected him and so there was no one who acompanied him in his struggle.
Left alone in his weakness and illness, he struggles with existence and develop a philosophy of conflict, competition, fight but also of the love of aestethic, music and art, of the joyful acceptance of life itself and the beauty and joy the universe hand down to us.
Nietzsche realized that the realities of life, our joy, our pain, our limits are not only part of our existence but also part of our thinking and percieving life. The mind and the body are a unity which cannot seperate and the reality of life which ones percieve creates a very own universe. As a chronical ill person, Nietzsche feels the struggle for life a healthy, joyful person would never be able to feel and experience of this universe in permanent change and interchange with every within fighting for its live and meaning.
His philosophy is a direct reflection of the dance of live and death, of creation and destruction, of meaning and insignificance. Even in his early work "The birth of tragedy out of the spirit of music" handle the subject of the apollonian and the dionysian principle as counterparts of humankind and civilisation between logic and extasy, order and chaos, the ego and the disolving of the ego.
His contemporaries experienced him as ill, strange, weak, weird and lone. He didn´t get the attention his works recieved after his death until the present day and in my opinion this aphorism mirrors that in an execellent way:
"And those who were seen dancing were thought to be insane by those who could not hear the music."