There are a few ways to secure your private key. You can use a hardware wallet, an encrypted device that stores private keys for all the coins you own. You can store an encrypted private key on a flash drive and keep it in a secure box at the bank as a backup.
You can also use encryption software, such as 1password, to store your private keys.
If you trade regularly, you will need access to your key often, so encryption software is a safe option.