Sounds like classic imposter syndrome. I've dealt with it at times myself. The best cure I've found is taking on a tough task, breaking it down to more manageable chunks, and completing them. Even after completing some tough projects, I still feel the fear grip me. I took a new job recently that required working with an unfamiliar framework and design patterns. Early on, I kept running into road blocks and thought for sure that everyone would think I couldn't hack it. Turns out everyone was actually impressed that I was picking up on things quickly. Just because you perceive something, doesn't mean others perceive it the same way. Go for it, and ask for feedback early (just don't get too hurt if they have something negative/constructive to say. Remember you can't be perfect)