It is crucial that your wallet backup is stored in a secure location. If anyone gets access to your backup, they can restore your wallet and potentially steal your funds. Depending on the value you’re securing, choose an appropriate location, for example a locked drawer, a safe at home or a safety deposit box.
The physical security of your backup is more important than that of your hardware wallet. The BitBox02 is designed to protect your cryptocurrencies even in the hand of a thief, but a backup allows direct access to your funds.
To further protect your wallet backup, you can use the optional passphrase. This is an advanced user feature, so make sure to read this entry first: What is an optional wallet passphrase?