There is a difference between being selfish and being self-focused. Suppose you have a throbbing knee after a workout. Is going to the sports medicine clinic selfish? No; it is an issue of self-care. Being motivated to be psychologically more healthy upon forgiving is similar. Your motivation of self-focused care may change to a different motivation as you proceed with the forgiveness process. Your motivation may then include the other person, as you develop a concern for this person’s well-being.
For additional information, see Forgiveness for Individuals.