In other words, try to only listen to the positive voices in your head. Unless they're telling you you can fly, and the negative voices are saying, "No, you idiot, you can't." Then you should listen to the negative voices, because you aren't a bird. At least, you weren't the last time I checked. If you've mutated into a bird since I last saw you, you really should have let me know.
Laugh at yourself often. Find the humor in whatever situation you’re in. Optimism is a happiness magnet. If you stay positive, good things and good people will be drawn to you. -- read: http://www.marcandangel.com/2015/05/24/40-powerful-mantras-to-help-you-think-positive/