Sometimes we don't realize truly how good something was til it is gone...
But also also sometimes it's fear of the unknown. Our past memories both good and bad can be security blankets of our mind...safe and warm...it's hard sometimes to not wish to go back....but no one has invented a time machine yet...so the only option is to choose a path forward or become frozen by fear....
I think if you are feeling regrets maybe you should talk to your ex wife about it...losing someone you once we're in love with is very hard..but depending on the 2 people sometimes a new kinda of love can grow. Not saying romantically necessarily but as friends/ family.
Every situation is different so I don't know if any of that is possible for you and her or not....
It just in my personal view of life...if you had a true deep connection with someone. They always will occupy some part of your heart.. so if there's a way to foster that connection without causing further harm to each other...it's always worth exploring (just my humble opinion) *I am a,hopeless romatic, dreamer and true believer in "happily ever after"**sigh*...sorry if I went off into my own fantasy world there. Pardon the intrusion. But hope whatever path you choice leads you to health and happiness