Don't put yourself down – there are more than enough people in the world who will be happy to do it for you.
Be mindful of the words that come out of your mouth. Look for the good in yourself and others, and use positive words to reinforce that behavior. The world could use more positive reinforcement.
Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear.