Learning my limits the hard way

Sunday , my hubby and I set out to finish 12.5 miles, in training for a half marathon on October 16. I was feeling positive and strong and enjoying the cool weather.
I was a bit concerned about right knee soreness I had last Sunday after 4 miles, so we started out slow and mixed in lots of walking for the first few miles. I felt some twinges in my left and right knees, but they seemed to go away with periodic stopping and stretching.
But around mile 8, my right knee was starting to feel sore. Not painful, but definitely sore.
Around mile 10, it was downright sore, bordering on pain. Like an idiot, I did not stop. I keep plowing through, thinking that I would just stretch it out afterward. BIG MISTAKE.
Just as I was nearing the end, my right knee told me in no uncertain terms that I needed to stop. It did that through a sudden sharp pain that virtually locked up that leg and required me to limp on my left leg for the last few hundred feet.
I dragged myself into the house, grabbed an ice pack, and a handful of ibuprofen. The pain lessened, but I hobbled around gingerly the rest of the day trying not to think about the fact that I probably won't be able to run again for days, maybe weeks. Which would pretty much kill my hope of finishing the race a month from now.
Today, I can walk, sort of, but resuming my training tomorrow is out of the question. Probably out of the question for the rest of the week. Maybe for the rest of the month.
I am a bit depressed about the whole thing, but I am more angry at myself for trying to "push through the pain." If I've learned nothing else from Coach Nancy and the other experienced runners here, I know that pain is a red flag that should not be ignored.
I have learned a lesson that I will not soon forget about recognizing the difference between ordinary sore muscles and the real pain of an injury. But the most important lesson I have learned is that I need to slow down, maybe get a few more shorter races under my fuel belt before I tackle a big one.
So, I'm down, but not out. I am a runner, but maybe not a marathoner yet.
How about a nice Turkey Trot?