I totally understand your feelings. I had a crappy run 2 weeks ago and I completely killed my mojo. I am planning to do full in March so official training doesn't start until Nov., but I consider myself in pre-training mode. When I didn't finish my 16 miler, I thought if I can't do this, how am going to go another 10 miles. I felt defeated. The next day my period started. I blame AF for my craziness and yours. She's an evil bitch that plays on your emotions. You can do this!! Like @cseale said, 4.5 weeks, then taper. Take it one week at a time. I am also reading Advanced Marathoning right now (plan to use the Pfitz 18/55 plan) but am reading the whole book cover to cover. I just read about overtraining and a lot of the mistakes people make when training (not saying you are doing this but I know I do this all the time). I run too hard on my easy days and not hard enough on my hard days. This doesn't help with training and can lead to fatigue. Make sure your easy runs are easy, effortless. It will help with those hard workouts. You got this T! Boston 2016!!!
Take a couple of days to think about whether you're in a better position to keep training for the full in December, or take a short break and gear up for another training cycle next year. I wouldn't call it "giving up." I'd call it postponing things. Either decision is understandable, and we'll support you either way.
This is what I would recommend too. Take a couple days and see how you feel. Once you give yourself permission to not race the full (b/c fuck yeah 1/2's are fun too!), you may decide you really want to do it. In that case, game on! You've got this!
In a case of truly being over trained and not having your heart in it, I wouldn't do it. I've done that, and it made for a pretty miserable marathon and a year of trying to recover physically and mentally. Mine involved a last minute race cancellation, and then extending my training 6 weeks. I wasn't into it and probably should have gone for a nice half PR.
In any case, take a few days off, change things up a little. Follow your own heart, and don't worry about what anyone else would do. You're a smart lady and we've got your back!