You are such a good detector for the under tones.

Yes, when I thought of the chocolate I also saw the two qualities in it.

An affair can truly be connected to the "bad times" two people promise each other to go through.

From what I think, the vow must be very sincere and openly spoken with the most authenticity "I will love you. You can count on my love and I will wish you always to be well."

So, yes, I am not thinking a relationship must end but can enter a next phase. As I believe that the one who goes outwards does so because the other was absent or passive or not engaged enough - also not interested in himself. Sadly, many couples are not willing to make the repair work as it is too much of an insult for the ego. But I think here is a great chance to integrate what has not matured yet and the insult is really a huge opportunity to work on. For the out-goer it also is a chance to become more consistent and to find more trust within himself and not to stroke his ego with the admiration and seduction of something new.

But: Many couples do repair what got broken and it's wonderful to witness that.

For your last question: What a good one that is!
Dancing can cure a couple, I often think. To do co-creating stuff together and enjoy and celebrate where the intersections can be found has potential to help the couple heal themselves.

The most work, though, happens in each person on an intimate and self reflecting, contemplating level.