I need some good reasons for why ("normal") sex isn't a bad/gross thing one needs to avoid when in a loving relationship with someone, whether it be very long term (even including marriage) or shorter term.
one-night stand reasons need not apply.
None of these reasons either:
I would like some practical reasons for why it's actually useful for the relationship, as well as for the people involved with it. I also would like reasons for why jacking off isn't in the same league as sex within a stable and loving relationship (even though jacking off isn't a bad thing to do at all).
Most of you seem to be a clever bunch, I'd be happy and grateful for any help with this issue. I hope it isn't a too tall order.