Not safe of course

Even yesterday the biggest ever hack from exchange happened
https://www.coindesk.com/coincheck-confirms-crypto-hack-loss-larger-than-mt-gox/

You shoud keep some basics rules about managining your BTC & altcoins

Rule 1: A True HODLer Does Not Sell Their Coin.
Rule 2: A True HODLer Buys the Dip.
Rule 3: A True HODLer Remains Steadfast In Spite of FUD.
Rule 4: A True HODLer Keeps Their Coins Off Exchanges and Online Wallets.
Rule 5: A True HODLer Buys Goods and Services With Their Coin.
Rule 6: A True HODLer Spreads the Good Word.
Rule 7: A True HODLer Does Not Get FOMO When Another Coin Rises.
Rule 8: A True HODLer Will Run Their Own Full Node.