It is in the nature of human beings to be self-regarding, which is perhaps best. For the vast majority of people, if not everyone, knowing yourself and what is best for you is pretty obvious a conclusion. It is not selfishness, mind you, but consideration of oneself and your own interests. Selfishness would be the consideration of yourself without regard to anyone else or their interests.
Of course, one can be selfish without realizing it. You can be so obsessed with your own thoughts, or feelings or desires that you do not even think of anything else. You are not consciously disregarding others in your thinking; it just doesn’t enter your mind.
I got a reminder of this just recently when I found out someone I knew had been dealing with the terminal illness of a close relative. Suddenly issues I had been “dealing with” seemed, well, no, WERE, pretty petty in comparison.
The relative has passed away.
I will send my condolences and make sure to deliver a slap upside my own head to make sure what I wrote above sinks in.