“As Carl Jung said, avoidance of legitimate suffering is the root of all mental illness. And one truth you must suffer is that everything and everyone you love will eventually die.
Even gods.”

Source: The Seven Storey Mountain (1948)
Context: Indeed, the truth that many people never understand, until it is too late, is that the more you try to avoid suffering, the more you suffer, because smaller and more insignificant things begin to torture you, in proportion to your fear of being hurt. The one who does most to avoid suffering is, in the end, the one who suffers the most: and his suffering comes to him from things so little and so trivial that one can say that it is no longer objective at all. It is his own existence, his own being, that is at once the subject and the source of his pain, and his very existence and consciousness is his greatest torture.

Peter Camenzind (1904)

He Who Lets Us Be: A Theology of Love (1975), p. 4

Source: Les Misérables

Many sources attribute this quote to Brown without giving a specific reference to her writings. The earliest located is the following variation from p. 47 of Musgrave Landing: Musings on the Writing Life by Susan Musgrave (1994), which Musgrave quotes as "Rita Mae Brown's warning": "If you become the kind of writer who calls forth heated emotional states, be careful. There are a lot of unbalanced people out there. The statistics on insanity are that one out of every four people is suffering from some form of mental illness. Think of your three best friends. If they're okay, then it's got to be you."
Disputed

Morarji Desai speaks about life and celibacy

Hour of Gold, Hour of Lead: Diaries and Letters of Anne Morrow Lindbergh, 1929-1932 (1973), p. 3
Source: Gift from the Sea
Context: I do not believe that sheer suffering teaches. If suffering alone taught, all the world would be wise, since everyone suffers. To suffering must be added mourning, understanding, patience, love, openness and the willingness to remain vulnerable. All these and other factors combined, if the circumstances are right, can teach and can lead to rebirth.