Strangely, you just have to decide absolutely out of nowhere to have confidence in yourself. Your line is "I'm not perfect but neither is anyone else, so I am going to take this God-given parcel of Marc gifts and run with it, and help me Jesus, because I am going to give it the best shot I possibly can and not get hung up about little mistakes."

It sounds dumb but nothing else will do. 'To those who have will be given more in abundance, and from those who don't have, even the little that they think they have will be taken away.' You have to vote for yourself as one of the ones who 'have,' and one vote is all that is needed to win. When you declare yourself elected, Jesus will be the first to raise up his arm in triumph with you.

(What can interfere with this a lot is biological depression, where you just don't have the energy / oomph even if your cognitive mind is ready to be in the right place. That may need treatment if it's really the problem.)