I have enough different sites that for me moneywise this has been something of a zero sum change in my income.
I think you just have to expect rankings changes like this from time to time and not take it personally. I have had many sites lose half their traffic overnight in the past, a couple nice money earners had that happen this past week, and I'm sure it will happen many times in the future, too.
One thing you can plan on is that Bing may very well copy Google's algo change before too long, so you have to figure out what caused the drop soon or you'll be losing even more traffic within a few months. In fact I suspect part of the reason for the big change in Google was to try to differentiate their results from Bing. By labeling Bing a copycat lately, they are going to try to make it harder for Bing to mimic the new results without being very obvious about it.