Some people are content in the midst of deprivation and danger, while others are miserable despite having all the luck in the world. This is not to say that external circumstances do not matter. But it is your mind, rather than circumstances themselves, that determines the quality of your life. Your mind is the basis of everything you experience and of every contribution you make to the lives of others. Given this fact, it makes sense to train it.
— Waking Up: A Guide to Spirituality Without Religion
by Sam Harris