Selfishness

Selfishness is choosing to help yourself over someone else. Selflessness is choosing to help someone else over yourself. So if everyones life, happiness, and wellbeing are of equal value, then why is being selfish frowned upon? Aren't those things basicaly the same?

The only difference is that one helps you, and the other helps someone else. So isn't encouraging selflessness, in itself, a selfish act?