You are not alone with this feeling of anxiety. Especially at the start of every piece I wonder if I can pull it of or rather: Will I be able to create something that I am satisfied with?
I think it's a normal feeling as an artist, but acknowleding the feeling helps to overcome that fear of starting. It also helps to remember, that each and every piece is a step towards your goal of becoming better. If you see it that way, the outcome really doesn't matter that much.
Most important thing is to draw and having fun with it. Afterall you chose it as a hobby (or more) for a reason and the only way to regress is by doing nothing.
Looking forward to seeing new stuff from you =).