I paused. I knew the answer. I'd played over the very same question hours earlier, while biking. As it always did, the ride had provided a break for my brain, something which is both a blessing and a curse.
Was I sure? I concluded almost immediately that was the wrong question. I'd been asking the same question for most of my life, and the answer was always the same: no. But you don't grow as a person by sitting still, by waiting to be sure. You stagnate. I've had enough stagnation. Besides that, when I asked myself the same question, I realized that I was not apprehensive about the potential consequences of being wrong, and that in and of itself meant that perhaps subconsciously I WAS sure.
As he started to explain his question, thinking he offended me, I answered. "No. But I'm sure I want to move ahead."
Step 20: don't while away your life waiting for certainty. A sure thing is no such thing.