Learn to recognize when negative thoughts are creeping up. Think things through logically and avoid giving into overly critical thoughts.
For example, perhaps you get very nervous when meeting someone new. You might think that you’ll look foolish or say something to humiliate yourself.
When this happens, stop and think it through logically. If you say “hello” to someone and ask them a few questions to get to know them, are they really going to think that's foolish? People will probably find you articulate and intelligent.
Think about what you want to say to someone before you say it.