If this really is an individual who you're committed too for life, then I think there will always be that disconnect. If it's anything else, I would at least consider weighing the possibility of immense sexual gratification with the reality that you couldn't have that with your partner.
Also, this spawned a bit of a side question, but how do you... have sex with someone who's thin? I've tried before but legitimately can't. If you have any tips or advice I'd actually appreciate it.
Cheers