I really used to suffer from this until a fitter in a running shop pointed out that I wasn't lacing my shoes up tightly enough. Have followed this advice and not had problems since. May not work for you but might be worth a try?
I followed a training scheme for the half that took me up to 14 miles about a month before the half. Yes, it took it out of me but as a newbie runner it really gave me confidence to know that I could go the distance.
Have just run my first half marathon ( yey) which was my first ever race but, for various work related reasons, am not likely to enter another event for a while. My question is how to train now? I enjoy the long distances, but don't see myself moving up to the full marathon. So what do I do, now that I've built up to this distance I feel like I want to keep that ability, but would I be better dropping back for a bit e.g. to work on my speed for a while? Or should I repeat the training plan I've just followed and try and pick up the pace a bit? All advice gratefully received.