You gotta deal with it somehow. I think it may be some type of ongoing addiction to her in some degree. It's heathy to long for someone but hurtful if it takes your mind away from those in your family now.

My story is that I'm married - 14 years+ now. I did meet a similar deep love four years ago. Yes, it was an affair. Yes it was painful for all parties involved. Was an amazing time both for the bad and the good that came of it. After being with this woman, I didn't go more than a few hours without thinking of her for nearly 2 years. This year, she ended up getting married. On my birthday no less. I miss her dearly but know it was something way too impossible to do. I don't think of her as much, but we had and may still have an invisible mental connection (sort of a soul-mate kind of thing).

You can continue to think about her and have it pollute your mind with memories (which are great, of course) but you have to think of your current family and what they deserve - you. They need you to be there fully. You can work on trying to ease away from thinking of her and it'll eventually fade if you work at it. One recommedation is to seek out a therapist who can use EMDR with you. It helped me remove a long-lost feeling of loss for a young girlfriend (my first) from a long time ago that sounded a lot like your story. EMDR lets you let-go of some of these deep-seated feelings. it does work.