I agree you really can't let your own insecurities stand in your way. I know this is easier said than done. I've been questioning myself for being in college but I know it's important to me and I do want to learn. I only question myself because I, too, am scared of failure and inadequacy in every sense... such as work, friends, relationships and of course school. Don't let SA control your life. You can do it. Tell yourself that. If you enjoy science and are working your butt off as you say, you must want something out of it. Stick to it. It will be worth it.