So it can be the case that no one takes the 10 percent loss. Everyone who is selling may have bought at a lower cost basis (and thus will realize a gain). The price is lower because it had to go down to entice new buyers to bet it will go back up again.
There is a funky situation where you try to sell your assets and you find nobody willing to take it at any price. At that point, you can turn around and say "I don't want to own this worthless piece of paper anymore," strike it from your assets list (i.e., "write-off"), and now you realize a 100% loss.
If BTC loses 10 percent of its value overnight, the people who lose are the people who sold at the lower prices. When we say "the price of BTC is X", what we really mean is that a trade happened at that price. That means that someone thought selling at that price was the right thing for them to do and someone else thought that buying at that price was the right thing to do.