You are thinking too much. If your idea excited you, just get to it. Stop thinking if you can do it or not, just start trying and see if you enjoy the process.
Fair point - also, the law of sunk costs. What is past is past, ideally I should only look forward (except for learning from mistakes). It's not always easy not to worry, though.
Worrying is fine. It's how you find problems. If you worry to the point of not acting, you won't last very long. The process of finding and solving problems doesn't have much room for delay in the context of entrepreneurship.