Who do you think your biggest enemy is? Would you be surprised if we told you that your biggest enemy is yourself? It may be startling and it’s probably true; but that doesn’t mean that you are doomed to never succeed.
Once you recognize that you are the most likely person to pull yourself down, then you can proceed accordingly. Once you know your tendencies for self-doubt, you can focus your energy on being positive and building yourself up. There are already enough people that are working against you. Don’t add to the opposition. Don’t be your enemy; be your own hero!