You have to let him go. This doesn't mean that you have given up. You can still hope and try from a distance. At least that is what I think. If he wants to he will return. The point is that holding on tightly will not work. In their mind they have already checked out and there is nothing you can do about that.Sometimes you have to be apart to come back together.Hopefully both having worked on yourselves and being better than ever. Not that it is easy but there is really no other option.
Let go and let God. Not easy at first but it will come.
You cannot control life or him. Ever. So go with the flow. Not against it. Observe from a distance.Focus on YOU.
This is what is working for me. I will let others give their input.
