Some confidence comes simply from surviving enough ordinary mistakes.

A lot of what looks like confidence is simply having made enough ordinary mistakes to know that they are survivable. Not competence exactly, just the absence of catastrophic expectations. You have been embarrassed before and it did not end anything.

If you are stuck through fear of getting something wrong, count the times you have already been wrong and are still here. That evidence is more persuasive than encouragement, and it belongs to you rather than to anyone reassuring you.