The shape
Long and memorable beats short and clever.
Substituting a 3 for an E does very little. Length does a great deal. A sequence of four or five unrelated words is both far harder to guess and far easier to keep in your head than a mangled single word.
Pick words that are not connected to each other or to you, not your street, not your dog, not a line anyone has heard you say. Random is the property that matters; a dice roll or your phone's generator does this better than intuition.
Then use it. A password you type occasionally survives; one you set and never touch for a year is a password you are hoping about.
Method
A routine that holds up.
-
I
Four or five words
Unrelated, ordinary, and yours. Add a number or symbol if a rule demands it, not because it feels stronger.
-
II
Never reused
This password protects the vault and nothing else. It must not appear anywhere another service could leak it.
-
III
Rehearsed
Open a card once a month for the first few months. Recall, not storage, is what fails.
-
IV
Escrowed, not filed
If someone must eventually have it, seal it and place it separately, with a lawyer, or in a letter. Never in the drawer with the cards.
No reset link.
That is the point.MI8OS cannot recover a forgotten password and would not want the ability. Write the vault, then make sure you can still open it next year.