I went from 4800 miles per year to 10-20 miles per month due to repeated illnesses. Yesterday was a breakthrough ... I did a second ride in a week, and in fact, the day after the first ride of the month. (23 miles total.)
Just a long, slow recovery ahead ... no stress. After having my heart nearly explode 12 years ago, and coming back from that, I know that it is just a matter of keeping at it. The mental issue is the hardest .... like others, i try to appreciate what I can do and not stress over what I wish i could do or used to do.