This is the reason why we should choose a good and reliable exchange to trade, if you're deciding to trade, you must know those consequences waiting ahead and risk is a part of it.  Upon choosing to exchange and deposit your fund as capital, it means you already trusted them for any cost, for better and for worst.  

How many exchanges offer this service? (SAFU) Secure Asset Fund for Users , I think this will have a guarantee to traders to have a safe fund, but it doesn't mean, leave your fund and let sleep on the exchange.  After trading, don't leave your fund on an exchange platform that you have used, if you will see net profit was there and already covered by the withdrawal fees, you can withdraw them all.

So basically, we shouldn't leave fund on CEXs and custodial wallet, the line that you've used, Not your key, Not your coin is a great warning to all newbies who wanted to join the crypto space.