Trading is already dangerous enough, if you try to short the market or use leverage then you are basically guaranteeing you are never going to see your money back, the asymmetry of the market is there to play against you, technically speaking there is no limit to how high the price of any coin will go while at most while you short you can only earn 100% of your capital, do you see the problem?

Then add the volatility of altcoins to the mix and you have a combination so dangerous it will be almost impossible to not lose your money, which is precisely what happened to you.