I don' know if there's some magical tally keeping track of our good and bad actions but I believe in a form of karma.
Most people who are jackasses tend to be unhappy. They treat people like crap, are despised for it by others and usually don't like themselves. They may or may not have nice stuff, but I don't see too many who are truly happy.
People who are good to others often have lots of real friends (opposed to fair weather friends) and can find things to enjoy where they are. You may get dumped on by the world but having real friends and finding happiness where you are makes for a good life.