Just as our income is decided on Rosh Hashanah, so are our losses.
Hashem allows monetary losses to serve as a kapparah for decrees. So, for example, if someone is supposed to break a leg, he might instead lose $100. That loss would serve as kapparah; the pain Hashem inflicted on him is in truth a chessed.
However, a more beneficial way to lose that money is by giving tzedakah. If we are going to lose it one way – e.g., in the stock market, or another way – e.g., when the rabbi calls for a donation, surely we would rather the latter.
Not only will you earn a kapparah, but you will turn the monetary loss into a spiritual gain!
~ R’ David Sutton