If you have not been running for a few months DO NOT come back and try to immediately pick up where you left off! In my case doing 3 x consecutive days of running, as well as doing a half marathon training run without a proper build-up has hurt my left knee and lowered my morale.
I have now had to take more than a week off running to rest. I need to come back slowly and hope I can build up enough to take part in the Hardmoors 30 miler on New Years Day!