I think that when we grieve the loss of a relationship, no matter how toxic it was, we are also grieving for the life we expected to have.
As others have said, ride the grief wave, don’t turn it away or stuff it, post here, journal, go for walks or runs, and just live your life day by day.
And I wouldn’t count on everything being roses and unicorns with the new family.
You have peeked behind that curtain.
If you want a happy ending, that depends, of course, on where you stop your story.