How the hell do people have so much confidence in their ideas? Is that a skill you learn?

I don't get it. I'm a person of few skills. I can make stuff, drawings mostly. Any time I have an idea of how to use said skill for profit, I talk myself out of it. Plan on doing RedBubble as it seems there's no risk. But currently I've been toying with the idea of selling painted terracotta pots at street fairs, and offering cuttings of my plants. It seems like an enjoyable thing to do that might get a small amount of money. But immediately I start thinking, "no one is going to care about pots." Or "You'll never produce enough to sell and just get burnt out." And I dread telling people in my personal life im going to do something, and either not following though, or failing completely. see hubwealthy.com/wealthy