From The Gulag Archipelago:

Do not pursue what is illusory–property, position, all that is gained at the expense of your nerves, decade after decade, and is confiscated in one fell night. Live with a steady superiority over life–don't be afraid of misfortune and do not yearn after happiness; it is, after all, all the same–the bitter doesn't last forever and the sweet never fills the cup to overflowing.

It is enough if you don't freeze in the cold, if thirst and hunger don't claw at your insides. If your back isn't broken, if your feet can walk, if your arms bend, if both eyes can see, and if both ears can hear, then whom should you envy? And why? Our envy of others devours us most of all.

Rub your eyes and purify your heart–and prize above all else in the world those who love you and wish you well. Do not hurt them or scold them, and never part with them in anger; after all, you simply do not know, it may be your last act.