life is so complicated

how do you know if you have crossed the boundary from being "just nice" to being a people-pleaser? isn't it still stand true - the fact that if you are nice to people, then they are nice to you? how do you know if you have turned into a doormat when you are just trying to be considerate? life is so complicating and filled with things i just simply do not understand. feels so confused now. and I am only 20 years old, yet feels like the burden of the world on me.