Does this person represent something that was lacking in your current marriage?

Your fantasies are actually going to be the key to this if you allow yourself to think about it.

There's that whole "grass is always greener on the other side" deal too, no relationship will ever be problem free. If you have been compromising in your relationship, or you two are not allowing each other to be who you are as individually to the fulliest level, that's gonna mess things up and leave you wishing you had someone who was "more this" "did that" or "never was like this", ect.

so a place to start would be to ask yourself what made you like this other person, what is it about this person you still think about.

Every human has needs..are yours being met?

Take care,
-obj