Today is the ninth day since I last went out and ran. My hamstrings (the right one in particular) have been tender on and off since last November but it hasn't affected me terribly.
Lately, that has started to change. I've been running suicide sprints with my daughter's basketball team trying to motivate them by getting them to "beat the fat old man." Every time I run the sprints, the next day my hamstrings (left and right) are killing me. I'll go easy on them by not running for a couple of days and then I'll try the sprints again. My regular runs are also getting embarrassingly slow because my stride is shortening up to compensate for the pain.
I'm hoping to get a bike trainer later this week so that I can continue to train by doing some bike riding while I give my hamstrings some time to heal. I guess the lesson to be had is: Learn from your past experience. Don't continue to try and do something that you know is going to hurt you and expect a different result.