The security bottom line of self-custody wallets is actually very simple: the mnemonic phrase should always be stored only on your own device, and must never be shared, backed up to the cloud, or exposed to third parties.

Once this boundary is loosened, trouble arises. Mnemonic leaks, screenshots, cloud backup records—if any of these steps go wrong, your assets are essentially exposed to risk. Not to mention those seemingly convenient wallet custody services, which on the surface help you manage your assets but in reality are equivalent to handing over your private keys to others.

Therefore, to truly control your assets, you must maintain this boundary. Local device, known only to you, with no backup vulnerabilities—these three points are indispensable.