Take the hits and keep moving forward.

[T1000]

This is how I'm thinking of responding:

I can assure you I took the separation very seriously.
I was very upset when you left. I decided if it could be saved it was worth saving. I wanted to keep our family together.
I didn't view it as the end of our relationship. Every time we interacted, went on vacation, slept with each other and had fun with the kids during our separation it gave me hope that it wasn't the end.