Your ego could be a source of trouble if it becomes too big. Other people could have trouble interacting with you because they may feel as though you're too focused on yourself.
It could be if all you think about is yourself. Dedicate time to doing good things for other people, and you'll feel better than when doing things for yourself.
Not necessarily if it helps you to succeed for the purpose of helping others; if you succeed for your own purposes and berate others in the process, then it is.
