The 62% retrace is a very rough figure. You got each of the big trading houses working off their own models. It generally coalesces around the main fibs, but not always. After the flash crash (may 2010) we had a much larger retracement than 62%. But it still sold off and retested the intraday low set during the middle of the flash crash. That's just what markets do, most of the time. Certainly not always. Things could be different this time. Sure, we could rally all the way to new highs, and then blow those out by 10% before its done. If enough people are shorting the market, then there is all that much more money that can be turned back around on them. That's how it works. That's why most shorts usually lose money, because the guys in the big trading houses can see how much money is short, and can easily calculate how much it would take to stop them all out and wipe them all out. And they can borrow the money to go and do it. In order to have a really big selloff, we got to have most people long and bullish. It just seems with QE ending that too many people might be bearish. At any rate I personally only short using up to 20% of the profits from my last long trade. To put any more than that up is foolish because no one knows how big these snapback rallies can be. Except for the guys borrowing billions from the NY Fed at 0% interest and using that money to buy e mini futures by the boatload. And if they lose it all? Then so what. Its just a number on the balance sheet to them. If that number gets too big then they go get a bailout. That's why its foolish to bet against them most of the time. You gotta have a lot of experience and follow very specific rules, no matter what.