it looks like we all have keys, passphrases or even fingerprints. But it seems that it is not really safe. Lots of coins stolen every year, millions of dollars. I like to keep my money at Leger, I feel safe, I don't trust the internet, the browsers I'm using. The keys I wrote on the paper and put it in the safe. It is safe
It is not 100% safe if your coins are kept in online wallets or even desktop wallets. The internet is indeed full of hackers lurking around, waiting for any prey. If I know, right at this very moment, some hackers are doing attempts to get inside the safety walls of wallets. Hot wallets are more prone to such attempts than cold wallets. But if you don't have much choice, keeping private keys on a piece of paper is much safer than storing the keys in laptops and PCs. Just make sure you have several copies saved in different safe places.
But of course, Ledger Nano as well as Trezor are the most common and best choices of hard wallets.
In principle, if you are careful enough, this will be enough. Of course, if you need to leave the coins for long-term storage, it is better to reset them on a physical storage media such as a flash drive. 
