I am currently training for 10k and continously have the same problem. I seem to train and run really well for a few weeks and then I seem to just loose the plot compelely. Then I feel like I'm starting from scratch all over again. I've tried loads of different approaches - at moment I'm using one of the schedules off this website. I feel like I am coping with it well and following it properly (which I admit has been a problem in the past) but last week I still felt like I couldn't put one foot in front of the other.