This is hard because you have the memories of the good parts. But if it has changed, feels bad, is becoming hurtful or toxic to you, sadly, for your own sake you need to let it go.

I am going through this right now. My friend & I mutually & simultaneously let go, then after a year I started getting contacted again. I was glad and tried to be happy about it, but I was cautious. Then all the bad energy started up again, as I feared it would. There is a sort of 'human vortex'/ 'toxic black hole' aspect I just cannot tolerate anymore.
Now I am being less available. I have to protect me first... I need my energy for me...