You can use software that allows you to create a wallet with a seed phrase of 12 words.
It's not impossible to remember 12 words if they are very important. This way you can keep the wallet in your brain. Also known as a bitcoin brainwallet. No one can steal your thoughts.
In cryptography we trust (& verify).
I have considered a 'brainwallet' before but I think the key is to refresh those words regularly
as in to make sure you are remembering the correct words.
In the case of war where you have to vacate you home or that you cannot actually get to
your home a brainwallet is the only thing which is going to save you..