When I was encrypting stuff (I quit because it was just too much trouble considering I’m pure as the driven snow, and nothing illegal is on my computer), I invented a phrase containing both capitals and lower-case letters, symbols, and numbers, that would mean absolutely nothing to anyone else, but was easy for me to memorize.
Hard to say what it would be for you, but I suggest literary references, personal experiences, or even some dream you had that you still remember.
Jesus? Is that you?? Why the long wait to return to us?