Perhaps a mark on your character that you feel difficult to remove. Also marks left in some way that tell others about you.
Example: I am to teach and I am wearing this big khaki outfit with a big shirt that goes over my belt. (I am very fat here.) And there is a huge wet pee stain that I just discover by looking into the mirror before I go in to teach. Others can see it fairly easily.
Example: Will he smell the fact that I’m on my period? Will I stain the sheets? What if I want to masturbate?”
Example: I had to get up and wash my penis. It felt dirty with the stain of an awful thing. I had to wash it off. I got up and did this. Gradually the reason for all this clarified. It was that I was experiencing the awfulness of sex without love, the dirtiness of using somebody else’s body.
As can be seen from the examples, one can use stains in very different ways. They can be used on paper money to detect a thief, or even in ones body to see its workings or disease.