Now all the markets are crashing down and I don't know what to do with my altcoins. My briefcase fell 30% in a couple of days. I'm afraid I might lose more. Selling or hodl?
Absolutely obvious on what you should do like this situation in the Crypto, HOLD.
Sell if you don't want to lost the half your capital and the half was lost.
Hold if you want to get back your capital and have a big profits, i believe it will recover soon as possible.