I agree that for the most part we are self-interested. But if you define rationality as this logical, analytical, unchanging, unemotional approach, then we are irrational. And I hate that we have given it this term. I think that those unselfish, emotional, etc. behaviors have their own rationality of existing. Take, altruism for example. It does not make sense when studied from this economic perspective. But if seen from a societal point of view, it is beneficial, therefore rational in its own way.