People are Self-Interested
Every single person you meet cares more about themselves than they do about you.
You don't need to by angry or resentful about this. Because you are like this too.
However, there are a couple important differences.
Some folks are solely self interested. That is, they will slit your throat, so to speak, for their own personal gain.
Other folks however, albeit self-interested, still have integrity, and have hearts, and care about others as well.
It is good to remember the different types of folks there are out there, and to consider which type of person you are.
And it is good to remember that people are generally self-interested. That is why it is good to take a genuine interest in other people, listen to them talk about themselves, and do kind, considerate, generous and helpful things for other people. This is how you make friends. And bets friends are the ones who reciprocate.