Just found this on another forum. I don't know if I'm allowed to do this, but it seems very pertinent to the mental block I'm having worrying about speed+distance, so I'm reposting it here (it's in response to someone having problems with Week 7).
"My advice, which is from my sister who has completed many marathons, is that you shouldn't be focusing on getting faster, instead you should actually allow yourself to go slower. That is actually probably why it was harder to finish on the treadmill, which keeps you at a more consistent pace. My sister told me that when I feel like walking I should just run slower--I told her I was running as slow as possible, but she said that even if I could walk faster, making the running motions helped my muscles learn and develop. I've found it really works--especially at the end of a run when I want to give up right before I should be done, if I just lower the speed I can work through it.
The good news is that as you run more your speed will increase naturally. Maybe not as fast as you'd like to end up, but faster than you are now. I run with my phone to track my time and distance running and I can say that I completed the c25k in June doing 12-13 minute miles, or even slower for some parts of the run, and now I can consistently do 10-11 minute miles, even on a 6 mile run! I would like to be faster, but my understanding is that I need to get a good base of miles run--adapt my muscles, tendons, bones, etc to the strain of running before I push too hard. The one tip for speed I have adopted is to add a few hills into at least one run a week. Not hill workouts, just varying the incline."
Isn't that brilliant advice? well.. it's made me feel a lot happier anyway!