•Selfishness is not using others, or making them serve you, or removing yourself from people. Selfishness is being primarily interested in your own goals. Selfishness has nothing to do with other people - a selfish person who hurts others is a contradiction in terms. A selfish person is concerned with their self, and has no need to hurt others.
•With the possible exception of your parents, no one else is looking out for you (and your parents may get it wrong sometimes, even if they have good intentions). That means that you are the only one really on your side -- so it's your job to put you first! That's not being selfish -- it's being logical