I am very grateful to have the good relationship that I have with my daughter's mom (I hate to call her an 'ex' anything). It often feels hard to explain and seems so far from the 'norm.' There shouldn't be a norm. Coexisting in a very conscious state of mutual respect is the only way that I can imagine divorce being tolerable and not an excruciating life experience.
This state is always something that I have had trouble putting into words. I recently saw an article in the NY Times that sums it up excellently. Please give this a read and see what you take away from it. It is possible. There is a conscious choice involved. I have heaps of respect for these folks, and I'm personally delighted to be living in a very similar scenario.
An Optimists Guide to Divorce from 11/24/17