What to do with a poem once you have memorized it

You can recite it in public or private situations, of course.  You can study it in your head and think about it, cite from it from memory when the subject comes up in conversation (which tends to be rarely). Waking up with some Keats in your head is a good thing. I like speaking it in the shower. If I wake up at night I can have a poem to recite to myself, or as I am trying to fall asleep.  Some phrase of it might resonate through a poem you are writing, or even in a translation from another language.