Let's say that for years you'd been wanting to rub baby ducks across your butt. Just to see if you'd like it. And you need a friend to do this with you because ducks are mean and you need help catching them.
So you and your friend go catch some ducks and get to butt rubbing. It was an okay experience so you get together and do it again a few weeks later. You decide that you've maybe had enough of this activity and would rather not do it again.
But your friend wants to keep catching ducks and wants you to play too. How is a nice way to say that you'd rather not partake in the activity that you introduced your friend to?