Self-interest is a set of situations that favor you. Selfishness is actualizing some of those situations without regard to who gets hurt. (I think). I think t

Self-interest is a set of situations that favor you. Selfishness is actualizing some of those situations without regard to who gets hurt. (I think). I think that what you are asking is something like: "How do you draw the line between reasonable pursuit of self-interest and unacceptable pursuit of self-interest at the expense of others." I don't think that there is a single answer just a set of rules that may or may not apply. One such rule might be "Weigh the size of your gain vs the size of the harm to others. Another might be "Weigh the gains and harms resulting from alternative choices". Your set of rules lies within your executive function which resolves such issues. For each of us the set of rules is certainly different but may have many similarities within a single culture. There are all sorts of complications. How do you value a situation that may have multiple positives and negatives. In the end, the choice is so complicated that the choice is often motivated by emotion because reason fails us.