It's probably just the same as remembering phone numbers. I just break them down into say 3 or 4 character combos until I have them all memorized. There's no way in hell I'd trust myself to solely rely on remembering an entire seed phrase though. I'd be terrified of forgetting. A safer backup way though maybe to split your seed into 2 or 3 parts and leave those with trusted family members or a friend. Maybe don't even tell them what it is or even conceal the phrase in some sort of text and tell them to keep that safe. At least if worse comes to worse and you did forget or you die you or someone else could restore them (and you could leave instructions with a lawyer on how to access them).