I wouldn't call it a fantasy, but one frequently recurring memory I have is the first time I purchased an enema bag. I scoped out the drug store for quite a few minutes before getting the nerve to buy a standard red douche/enema combination bag and a tube of K-Y.
I couldn't look the clerk in the eye because of the embarrassment. But I made the purchase anyway, knowing that the reward later, would outstrip the humiliation. It did!
I've come to realize that embarrassment/humiliation are part of the whole scene for me. I guess that's why that original purchase sticks with me, and comes to mind frequently.