The trick is breaking the cycle. My little death pony had me on his back and was telling me all kinds of lies about my failures, my upcoming failures, and my ultimate demise as a failure.
When one parent checks out their options for divorce, they are beginning the process of separation and exit from the relationship. And hey, if they like the divorce brochure the attorney lays before them, they might even start leaning into divorce.
Bless your co-parent just as they are. Let go of your expectations about co-parenting. Then parent as best you can. Release everyone, even yourself, from the expectations and dreams you had of a wonderful co-parenting relationship.