How do you let go of someone who you were truly in love with. Knowing you can't be with them anymore ...

Seeing as since he moved back to Germany and since we couldnt physically be together... He finds someone else and barely talks with me at all. Only sometime. How can I live with the fact that the only man I've ever loved... Loves someone else. I keep trying to walk away from it seeing as how he moved on... But its been 3 years now that I haven't seen him... Yet I still care about him like crazy. Or maybe its all in my head.... How do you get over this kind of love. Knowing he doesn't love me back. But will occasionally text me from time to time. I cry sometimes because all I have are the memories of us. Nothing more 💔