Psychological Egoism and Ethical Egoism

Human beings put so much value on other people's interests. They find that if they satisfy their hunger for helping others, they (in turn) will have satisfaction for themselves. This was shown in Mother Teresa's giving to others without taking anything back. However, as with everything else, there are exceptions. I know many people (i.e. car salesman ha-ha) that have only their interests in mind when they are taking action. This brings us to the discussion of the difference between psychological egoism and ethical egoism and my position upon ethical egoism.
…