Leo Tolstoy, translated by Maureen Cote
Excerpt from the Path of Life:
You should understand that if a person is unhappy, it is his own fault. Unhappy people are unhappy, because they want what they cannot have. Happy people are happy because they want what they can have. What is it that people cannot always get, even though they want it? And what can they always get when they want it? People cannot always get what is not under their control, and what does not belong to them, or what others can take from there. All these things are not under their control. People can only control what does not belong to anyone else and what cannot be disturbed.