I made this image up earlier today.  The straight lines are supposed to convey the 9 and 20 MA's, their slopes from very steep to less steep and flat or down.  

basically trying to convey that rarely do you get those big sell offs like I show on that bottom when when the MA's are slopped like that, unless it's blow off top or something parabolic. what tends to happen is people do indeed manage to catch a short, it works for a 1/2 day or a day, they don't take profits because they think the market should go lover because it's overbought, so it rebounds fast and they lose their profits

the point to take away if one does short when the MA's are sloping like that, take profits quickly vs holding out for a big trade that doesn't come.  Better to hold out for the bigger short when the MA's are more flatly sloped, or short the lower high from such a condition.

Also I added a current daily SPX with the SPX invisible so that you ONLY see the 9 and 20 MA, basically illustrates this whole point. I will add that it's losing some momentum but still quite steep and of course was really steep a month ago