Here’s the problem. Like @ChazMaz said, people assume that “selfishness” is a bad thing. However, it usually is.
This is the definition of selfishness: characterized by or manifesting concern or care only for oneself. The key here is “only”. I also believe definitions use “primarily” along with “only”. In other words, a selfish person is someone who cares mainly for themselves and neglects to care for others. We all display acts that are concerned with the self and are motivated by the self, but that doesn’t mean that we are all unconcerned with others. Many of the things we do are selfish because they concern ourselves and no one else. But many of the things we do are not.
When you do something kind for someone else, are you doing it because it makes you feel good or because it makes the other person feel good? I think that even if it makes you feel good, as long as you have concern for the other person and are satisfied with their satisfaction, then you are not “selfish” because you are doing it for them.
Either way, the term is thrown around way too much in an accusatory way and a hypocritical way, mainly because we all do things that have selfish motives, but we love to point it out when other people do it.
But yeah, I pretty much agree with Lincoln, but I don’t think he was meaning to say that all humans are only concerned with themselves. A truly selfish person does not care about other people, but most humans do care about at least one other person.