ABC of cuckoldry
D: Denial
Whenever you beg for a chance to cum, your hothusband/hotwife insists that their orgasm is just better when they know you're not having any. It makes theirs so much more special -- it's like they're cumming for both of you.
Of course, that also means that if you were to insist on being allowed to cum, you'd be taking pleasure away from them. It's a zero-sum game: every orgasm you have takes away from how much they can enjoy theirs. That's why you no longer fight your denial. It would be selfish to want to cum, and you could never deny your wife/husband a better orgasm.
Hence, you've come to accept your denial...