Ask HN: What would have stopped you starting your company?

For those of us that have started a company, what would have prevented you choosing to start in the first place?

Maybe it's resources? Maybe it's a mentor? Maybe it's support? Maybe it's your parents or the school you went to?

I wouldn't have started my previous company if I hadn't had support from my Mum "Your only young once, go do it", if I hadn't had a computer scince degree "Hey, do you think you could build our app?".