First, there is always the possibility that I could be wrong. The markets could hover around these levels and fall no further. Second, I may not know when to buy back in. Do I back in after they have fallen 10%? How about 20%? Should I wait till 25%? What if it goes down another 3% and then starts to head backup.. and then back down again above these levels before falling another 30%?

What you are suggesting is market timing. I am not very good at it, and I don't think most people are. You not only have to know when to sell, but you have to know when to buy back in. You have to get it right twice.