When we're constantly thinking about ourselves, our world shrinks.

You don't lose yourself being selfless—you find yourself.

Oh, my child, can you not see? You must let go of yourself. For if a seed wishes to live, it must sacrifice itself and grow outward, not inward.

To be happy, we must not be too concerned with others.

Indeed this gentleman's stoicism was of that not uncommon kind, which enables a man to bear with exemplary fortitude the afflictions of his friends, but renders him, by way of counterpoise, rather selfish and sensitive in respect of any that happen to befall himself.

Nature is infinitely rich and diverse in her ways. She can be seen to break her most unchanging laws. She has made self-interest the motive of all human action, but in the great host of men she produces ones who are strangely constituted, in whom selfishness is scarcely perceptible because they do not place their affections in themselves. Some are passionate about the sciences, others about the public good. They are as attached to the discoveries of others as if they themselves had made them, or to the institutions of public welfare and the state as if they derived benefit from them. This habit of not thinking of themselves influences the whole course of their lives. They don't know how to use other men for their profit. Fortune offers them opportunities which they do not think of taking up.
In nearly all men the self is almost never inactive. You will detect their self-interest in nearly all the advice they give you, in the services they do for you, in the contacts they make, in the friendships they form. They are deeply attached to the things which affect their interests however remotely, and are indifferent to all others. When they encounter a man who is indifferent to personal interest they cannot understand him. They suspect him of hidden motives, of affectation, or of insanity. They cast him from their bosom, revile him.