Fear. It can stop you from reaching your goals. It can make you lose sight of what is unique about you. Alot of us have issues with fear and it has handicapped many people who let fear take over them. They have stopped living and settled for "being safe" instead of really living.
The only way to beat fear is to challenge it – to not let it consume you. If you do let fear get to you it will tear you up from the inside and you might lose out on a lot of great opportunities.