I'm feeling pretty blue today myself, but will share my limited understanding of friendship with a walk away.
First and foremost is detachment. Get to a place where you realize you will be okay either way. Spouse can catch up, or not, their choice. You are going to start living life as "me" rather than "us".
Second, boundaries. Decide what you are prepared to tolerate. If spouse is informing you about dates, and you don't want to hear it, draw a firm line. You deserve to be treated respectfully. This goes for everything else. Protect yourself, lovingly.
Third, friendship with spouse. Realize you are not their best friend right now. Treat them with respect and kindness. Do not share your deepest thoughts/feelings, this is not the time for that. Rather, treat them as you would someone you know just a tad better than a stranger on the street. Distance your heart, but continue to be kind.
This is the hardest thing I've ever been through, but I am learning and growing. Reading these boards has broadened my understanding and knowledge more than I ever dreamed. For me, focusing on MY OWN journey has made the difference between completely giving up and moving forward. I CHOSE to move forward and become a better me.
