Anyone else feel like this sometimes? I go through this at LEAST once every book project. The insecurity helps keep me humble and also motivates me to always keep learning and experimenting, to push myself to step out of my comfort zone. I try to write or doodle in my journal every day, and will sometimes share my entries publicly. If you're looking for extra motivation to start journalling, I encourage you to check out National Journal Writing Month, which encourages journal writing for personal growth but especially in Jan, April, July and Oct.