It’s a hard lesson to learn. Just last month I ran in my first marathon and did pretty well (3:36:32). About a week after the marathon I thought I was on track to keep up some light running until my next training started. Then the Achilles tendon on my right foot started hurting. I kept running on it thinking I just needed to stretch more. Wrong. I had to completely stop running for over a week and limp around with my bum ankle.
Now, after two weeks with not much running I am running healthy again. I’m pretty sure the injury was a product of over-training so I am now doing more cross-training to keep up my cardio without killing my legs. I just hope that this was enough of a lesson that I will listen to my body more if/when another injury comes up.