Unsatisfied fantasy

I recently asked my wife for a mfm threesome or a situation where she had sex with another guy while I watched. May or may not join in but definitely be jacking off. I explained it is my fantasy but it involved her having a new experience with a new guy. she turned me down and since then I find it hard to get turned on knowing my fantasy can never happen. any advice on giving up on a fantasy that I wanted so bad. I actually dreamt about her fucking other men almost every night for what felt like months.