I read this recently, thought I'd share:

Self-doubts can be so overwhelming that nothing seems to help: even if others contradict your doubt, you can’t take it in. There are three basic approaches that you can use to stop labeling yourself as unreliable.

You can learn to better handle situations that set off your self-doubts. This means pinpointing the triggers to your self-doubts, and developing active ways to deal with the triggers rather than just succumbing to your self-doubt.

You can question the authority of your inner-critic. This involves taking a close look at how you view yourself and make sure you aren't allowing your inner-critic too much power.

You can actively try to use the self-doubt as a stimulus for growth. This means you use the self-doubt as information about how you should grow.