From a certain perspective, everything you do is selfish. Why do you do something “nice” for someone? Maybe you expect something in return. Maybe you’d feel guilty or socially awkward if you didn’t do it. Or maybe it just makes you feel good to do something nice. Whatever the case, you’re doing something because it somehow benefits you.
It’s human nature to categorize people. You put certain people in the selfish camp, and you put other people in the selfless camp. You then rank yourself accordingly, deciding where you measure up on the selfish/selfless meter. But consider: Whether you cheat on your spouse or buy him a present, you do so for some kind of personal benefit.
Once you recognize that all behavior is somehow selfishly motivated, resentment and judgment (of self and others) begin to loosen their white-knuckled grip. In fact, you could even make the point that the most skillfully and mindfully “selfish” person is often the one most likely to lend a hand. You get back what you put out. When you’re convinced of this basic truth, being generous becomes increasingly automatic.