Some people say Bitcoin is great to keep your money safe. I don't get that. A good way to keep your money safe means its value doesn't change much. But Bitcoin's value goes up and down a lot, so it's risky. Why trade the safety of government-backed insurance for something that can change so much?
With Bitcoin, if you use a non custodial wallet, you have private key and mnemonic seed, so you will have your own bank.
Being your own bank means you won't lose your bitcoin because of any centralized exchange, any bank. You always have your bitcoin, access to it, if you keep your device and wallet safely from hackers.
Bitcoin value and price can increase or decrease or drop to zero but it is another matter. Even Bitcoin price change, your portfolio value will change but you always have your bitcoin. It is what that advice means if you get its meaning.