Living with doubt
... is almost always more profitable than living with certainty.
People don't like doubt, so they pay money and give up opportunities to avoid it. Entrepreneurship is largely about living with doubt, as is creating just about any sort of art.
If you need reassurance, you're giving up quite a bit to get it.
On the other hand, if you can get in the habit of seeking out uncertainty, you'll have developed a great instinct.