We can't control most of the things that happen to us. We can't control other people. But we can control ourselves. If you find yourself thinking a certain way that makes you feel unhealthy or negative, then take a step back and change your thought.
It doesn't have to be an overly positive thought or an unbelievably optimistic thought - just one that makes you feel better. In a world where we look for control over events, others, food, we forget that we control ourselves. And that is a beautiful thing.