J: Jerking off
A rare reward, something never to be expected or demanded. Only your hotwife/hothusband or their bull get to decide. They don't owe you anything, yet a good cuck will likely occasionally be granted a treat.
Your orgasms -- if any -- are completely on their terms; that is: it will usually only be allowed under supervision, and meant to be degrading and humiliating. For example, they may tell you about how good other men are while you do jerk off, or sit on your face and have you eat other men's cum out of them. Of course, must always end with eating your own cum.
It should always remind you that your dick and your sexual pleasure are no longer your own.