Our beliefs come from the meanings we attribute to events. There is no inherent meaning in the things that happen to us, but we always draw meanings anyway. When I realised this, it helped me remove a lot of beliefs that were bringing me down. Instead of drawing negative conclusions from events in my life, I chose to frame them in a positive light and it just changed my life!
Another thing that helped me was when someone told me that there is a positive motive behind everything everyone does in the world. Before, I found it hard to get on with people but when I started putting myself in their shoes and saw what their motives were, it changed my whole viewpoint.
Ultimately, it's all about an attitude change. It seems simple, but I think if people just learnt to cultivate better attitudes the world would be such a better place. It's something they should teach in school!