Last year I overdid it. Too many workouts, too many long runs, too many races. I was doing a run and felt discomfort in the adductor, but it was mild enough to ignore. Two days later I did a workout and the adductor strained. Probably grade 1. Jogged home in some pain. Had a race scheduled for the Sunday, had a few days off and then did the race anyway. I got to start in the front pack and didn't want to miss out. As I set off I felt something go, which I now know was my adductor tendon. For about two weeks after it hurt to get up from a chair or swing my leg around to get in and out of a car. Attempted a run a few weeks later and bizzarely felt ok. Ran for the rest of the year. However I knew something was up as I always had discomfort on that side of my groin when trying to sit up. Had a rest of 6 weeks over Christmas and when I came back that's when the problems started. My groin would start to hurt after 20-30 minutes on every run and the pain would spread across to the other side. For a while I thought I had osteitis pubis. In reality the tendon was damaged and my muscles were detrained. To compound matters I also pulled my hamstring. At this point I had no choice but to rest. It took 14 weeks until I could sit up, lie down or turn over in bed without bed in the groin. First run back I managed 5 minutes at a shuffling pace before I fell over. My healed hamstring was so tight it felt almost rigid. I basically tripped over my own feet. 14 weeks of inactivity must have allowed a lot of scar tissue to form. There was, however, no pain in the groin. From then on it took about 6 weeks of rehab - building the runs up slowly and running without pain in my hamstrings which was acomplished by strengthening exercises. First I was able to do 3 miles without proximal hamstring teninopathy pain/sciatica shooting sensation, then 4 miles, then 6, 6 again and then 10. Did 30 miles last week for the first time since January. The thousands of miles I ran over the years have meant I have come back to form quickly. There's no tiredness or fatigue after 10 milers. After a long break I have regained some of my interest in running again. The most important thing has been being able to move and exercise without pain. The key for me was long rest (4-5 months), a very healthy diet, being very light and doing bodyweight strengthening exercises.
Definitely didn't overdo it on the paragraph usage in your post
I was just constantly in pain - crappy connective tissue, overtraining, terrible shoes - and the inability to train combined with not being able to keep up with the kids my age who were developing faster, I stopped hardcore racing after my Freshman year in HS. Every time I start back up, I would get overzealous and overtrain, getting injured again and again. So now, I am on a very slow build up as an over 50 runner with no fancy ideas of running for anything other than the love of it. I still want to improve but if I never run a sub 6 minute mile again, I'll be able to live with it.
Didn't fully quit but cut back to 10-15mpw when I got into weightlifting. I also do some rock climbing and cycling on the weekends with the kids. I look better, feel better, have more time, and and stronger. The only thing I miss about 80+ miles/week is being able to drink a lot of beer and still be slim.