When you short the most you can gain is 100% and that is if the crypto goes to zero. On the other hand if it goes up and you can't get out, you can lose everything you own.
My paycheck is in BCH. I constantly buy and sell in order to acquire *more* BCH. I only trade small amount. e.g. I'll sell $1,000 of BCH at $420 then buy it back at $320.
If you live in the U.S it just doesn't make sense to do that. If the profits bump you into the next tax bracket, then your profits are eaten up by taxes.