It makes no sense to worry about people who screw you over. They're not getting away with anything. People who lie and cheat may appear to have everything, but they do not have happiness. It's like they say in My Name Is Earl: "I'm the kind of guy who does nothing but bad things and then wonders why his life sucks." Karma works, and it works instantly. Don't let nasty people drag you down with them. If they deserve anything, it's compassion.