people are all selfish and think about themselves

I found recently that people are all selfish and think about themselves. I don't mean to blame for anybody who I know because I think I am one of this kind of animals and I am more selfish than anyone in the world. I just do things or say things which will be good for me and don't care about others. you must be wondering why I have this kind of thought. I can tell you why because if people don't think for his own good, then he will be kicked out of this cruel world.