"Happiness passes away, leaving hardly the slightest trace behind, indeed can scarcely be called happiness, since nothing lasting is gained. Unhappiness also passes away (and that is a great comfort), but leaves deep traces behind; and if we know how to improve them, of a most wholesome nature, and is often the cause of the highest happiness, as it purifies and strengthens the character. Then, again, in life it is worthy of special remark, that when we are not too anxious about happiness and unhappiness, but devote ourselves to the strict and unsparing performance of duty, then happiness comes of itself — nay, even springs from the midst of a life of troubles, and anxieties, and privations. This I have often observed in the case of women who have been married unhappily, but who would rather sink into the grave than abandon the position in which fate has placed them."
January 1, 1970
https://en.wikiquote.org/wiki/Wilhelm_von_Humboldt