It's basic but vital for all Bitcoin holders. They must learn about it and have enough knowledge and even practice with Bitcoin testnet in order to make sure that they can store bitcoin, secure their Bitcoin wallets, and wallet backups well enough.

How to back up a seed phrase ?
Not your keys, not your coins.

Don't use memory and brain. Don't split your wallet seed phrase because it's bad idea.
Why is seed splitting a bad idea ?

It's basic but vital for all Bitcoin holders. They must learn about it and have enough knowledge and even practice with Bitcoin testnet in order to make sure that they can store bitcoin, secure their Bitcoin wallets, and wallet backups well enough.

How to back up a seed phrase ?
Not your keys, not your coins.