Check out Dr. Andrew Huberman's podcast #1 on YT. "How Your Nervous System Works & Changes" He argues that feeling overwhelmed and the frustration of learning are necessary to activate the neuro-chemical processes needed to change our programming. Interpreting this emotional state as "doubt" is itself a mental program that can be changed when you realize that these neuro-chemical processess are necessary and normal. Also, get good sleep (which he covers too).