Without Jesus and our belief in Him, we would have NEVER gotten together and gotten married. It is through our belief in Him that we make our marriage work (or I should say He makes it work)
Hmmm...maybe that was way too broad...
My second choice would be: trust
We hide nothing from each other and we can read each other pretty well. We really are bad at lying (well I am the WORST poker player EVER! Hubby is pretty good at poker but can't lie to my face EVER! I really can tell when he is lying
He is a terrible actor!). We know we have each other's best interest at heart for everything we do.