well, along the lines of what havensov said, it's not only with mums. I mean, master had me masturbate every hour for a couple of days, and it was so frustrating I really had trouble concentrating on studying (let alone writing essays and meeting deadlines). The continuous teasing but not actually getting to cum can be really impractical at times because it can work both ways: constantly thinking about my pussy takes my mind off the book, yet constantly thinking about NOT studying doesn't allow me to let go. if it makes sense :-s