I have known my share of nice and nasty people.

Many of the nasty ones of my aquaintance have wound up in the end turning their lives into nasty hell-holes. Many of the nice ones have wound up with decent ones. Exceptions abound both ways of course. But I have never met someone who was both nasty and honestly satisfied with how their life had turned out. I have met nice ones who could say "I have no real regrets" and mean it.

Note that satisfaction and external success are orthogonal goals. Of the various people I have known who have achieved extremes of cultural success, not one has been able to get any real satisfaction from the accomplishment. That holds for both the nice and mean ones, albeit for different reasons.

Stop focussing on how you have been done wrong to. Stop talking about how many mean and nasty people there are. Start thinking long and hard about what matters to you, and how you are going to get it. Every time I wind up doing that I wind up telling my wife that I love her. YMMV (all things considered, I hope it does, after all you have your own!), but unless you focus on getting the basics right, nothing will really help.

Cheers,
Ben

To be sure, many mean people enjoy being mean.

That doesn't stop them from disliking dealing with the kind of people who are willing to be friends with them despite their being the kind of people they are. That doesn't make them feel better when they get in a fight at home.

While it doesn't always work out very fairly in the end, it does frequently enough that it is rather stupid in the end to be a mean person.

Cheers,
Ben