It hurts to find out your ideas are dumb, so you have to really want to know the truth more than you want to feel comfortable.
If I'm going to do my best work, I really need to love what I'm going to spend all day thinking about.
A lot of people want to make a product, not a business. What's the difference? The latter makes enough money to pay the bills. I get it: products are exciting; commerce is banal and a little grubby. But until it's a solid business, it's not sustainable.
Some people are really worried about what the competition thinks. Or what their friends will think. Or what's cool in Silicon Valley. Or even what their investors think. When instead they should be caring about what their users think, and whether they're staying true to their own vision.