I think I stumbled across the difference between true selfishness and protecting my self-interests.
If I am acting selfishly, I will do what makes me happy and take no responsibility for the outcome of my choice.
If I am acting out of self-interest, I am willing to take responsibility for my choice. Self-interest does not interfere with my ability to cooperate; it allows for mistakes. I can respond constructively to any situation my act of self-interest produces.
If I am acting out of selfishness, then I don’t care that someone else may be hurt, and if they are, I blame them for feeling the way they feel in order to diminish my influence and responsibility for the situation.
So when I “make myself happy” it isn’t that I don’t care what happens because of my decision. When I make myself happy, I do so from an inner point of what will help me retain my balance. Then, because I’ve maintained my inner balance, I can handle any consequence of my action compassionately, honestly, and with an inner willingness to change something if it needs to change.
If I act from a point of selfishness, I give up the ability to change. If I give up my ability to change, then I lose the opportunity to grow as a person. If I don’t grow, then I may as well be dead.
So, self-interest keeps me alive, keeps me moving forward, and ideally guides my decisions to help me become a better person.