I've typed up several snarkey personal-attack style responses but I'm just going to let it go with this point:

There are very few things that you know with 100% certainty beyond our own mortality. You have to weigh the risks and rewards and make a decision in almost everything you do, not only on the race course, but through life in general. With regards to racing, if you choose to make all of your decisions based on a certainty level of 100%, you will always be late to the start, you will always sail too far into a bad shift, you will always have too much room between you and your competition, and you will always finish at the back of the fleet.