Sometimes in a dream, I'll start running. I'll notice how magically effortless it feels. How wonderful to be able to run again. Then a little voice in the back of my head reminds me that this can't be real. It wakes me up every time.
It was a rough day when I opened Strava to log one of my physical therapy walks and realized that if I scroll down a bit, I can find a record of the longest run I will ever do.
I'm mostly at peace with it now. I'm grateful that at least I was into running for a while before I lost it, so at least I don't regret never having done it. And I never really enjoyed it then anyway. I just did it for health reasons and the sense of accomplishment.
I'm sorry for your suffering. I know what this longing feels like.