I'm Just Not That In to You

I don't know what's wrong. I began training for my first marathon attempt with such gusto.
I got some gear, new shoes, and started this blog to use as a training journal. This time I'm not so excited about what I'm doing. I've been here before. There's no real anticipation except the fear of getting injured again. Am I just waiting for the other shoe to drop? I'm supposed to do sixteen miles this weekend. Am I ready for it? I'm not sure. Do I care if I break down and walk part of it? Not so much. A few months ago, I would have felt defeated walking part of a long training run. Now it just gets me through. Am I training smarter not pushing to extremes or am I lazy and apathetic?
Maybe its the summer? Maybe the heat is hindering the extra spring in my step?