We all have ideas about ourselves that are founded in the opinions of other. If a significant person tells you often enough that you are "lazy, crazy, bad, or ugly" odds are good that you will come to believe it. Especially if it is something you are repeatedly exposed to in your childhood when the doorways to the unconscious are more open and malleable. Whether or not it is grounded in truth is irrelevant, for once you come to believe and act as if it is true, it continues to manifest as your reality.
Sometimes we have beliefs that are the result of a conclusion we made from an experience that we might not have interpreted correctly. Perhaps you failed at something, say hitting a softball. And because some ill behaved yahoos laughed, you decided that you were clumsy and would never be good at sports. So the more you thought about not being good at sport the more you missed the ball, the more they laughed, the more convinced you became, and the more 'true' that story became, eventually becoming part of your operating system.
Once a belief is established in the unconscious mind and becomes part of the operating system that runs your programs, it can be challenging to change it. Hypnosis and the energy psychologies can open direct contact with the unconscious and have demonstrated good success in rewriting limiting beliefs. The practice of mindfulness and somatic awareness can also open access to the unconscious and effect significant change. Whatever path you choose, think about what would happen if you released the misinformation that the world has told you about yourself and changed your story. How would your life be different? Perhaps you would find yourself to be artistic, graceful, brilliant, happy and talented in ways you have not yet imagined.
"Our deepest fear is not that we are inadequate. Our deepest fear is that we are powerful beyond measure. It is our light, not our darkness that most frightens us. We ask ourselves, Who am I to be brilliant, gorgeous, talented, fabulous? Actually, who are you not to be? You are a child of God. Your playing small does not serve the world. There is nothing enlightening about shrinking so that other people won't feel insecure around you. We are all meant to shine, as children do. We are born to manifest the glory of God that is within us. It's not just in some of us; it's in everyone. And as we let our own light shine, we unconsciously give other people permission to do the same. As we are liberated from out fear our presence automatically liberates others." Marianne Williamson, A Return to Love