There's a type of therapy called "Imago" that I found to be very useful -- for myself at least. It didn't do squat for the relationship.
:-(
I expect a good relationship would be strengthened by such therapy -- one of my best friends' marriage is much better for it.
Imago therapy recognizes that you have a 'model' of a relationship in your head that you probably got from your parents, and that colors everything you see in another person.
I recommend looking into it, especially where trust issues are involved.
http://www.airtonline.com/