On being self-centered

[JaBlue]

A lot of people say that being self-centered is a bad thing.

Why?

In some sense each individual is alone. Only he makes choices and only he is responsible for them. Does it follow that his fundamental - and only necessary - concern is how those choices effect him? If not, why should he worry about how those choices effect others in a way that is not rooted in his own happiness?

Why should anyone consider anything but their own well-being?