i lost bitcoin because trade, but since first time i know bitcoin i was never lost my bitcoin and my bitcoin still secure till now because i was never got hacked and exchange scammer, i hope i never get it
well you should never trust exchanges because such stuff can happen any time, after trading i always get back my money from it and i never leave it
if you want to trade bitcoin or altcoins you have to trust exchanges. there is no other way, you can withdraw your funds every time but you will end up leaving something on the exchange site at some point.