When a spouse walks away, it isn't usually a spur of the moment decision. The groundwork for her desire to be out of the relationship was laid bit by bit over many years.
She started out trusting you and believing in you. She started out knowing that you would love her and desire her presence in your life.
As the years went by and she found out time and again that what she believed was in fact not true...well...it changes people inside. She didn't wake up one morning and decide to go. She talked herself in to this being her only suitable response to life with you.
That's for damn sure the way it happens!
"Always go straight forward, and if you meet the devil, cut him in two and go between the pieces." - William Sturgis, clipper ship captain, 1830's.