I hold it like 99/1, 1% on exchanges obviously(spare change), And you should do that too. Anytime, the crypto exchange can just close and run away with your cryptocurrencies if they wanted to. Also, remember the previous hacks on bitfinex and Mt. Gox? Those events should already be a lesson for crypto holders.

News links for those interested:
Mt. Gox: https://www.wired.com/2014/03/bitcoin-exchange/
Bitfinex: https://btcmanager.com/bitfinex-confirm-64-million-hack-btc-usd-slumps/