Ask yourself whether a particular belief serves you. If so, keep it. If the belief keeps you stuck in a station of your life that you've outgrown, get rid of it and replace it with a more empowering belief.
Consistently remain aware of your beliefs about certain things in different contexts—for example, you can wear a rubber band around your wrist and snap it every time you catch yourself uttering something less than empowering. This will cause your mind to associate that belief with pain, and since the mind wants to avoid pain at all costs, eventually it will eliminate that belief. Make it a habit to eliminate the beliefs that you notice tend to be useless or that are holding you back. Make it a habit to believe even more strongly in the empowering ones.
Unstoppable Confidence: How to Use the Power of NLP to Be More Dynamic and Successful by Kent Sayre