Back running

I am trying to get back into running again with 2 days under my belt so far. I am try to follow a 20 week plan concentrating on time versus mileage. There is a race at the end of September that I am looking at doing. I am thinking of shooting for the 50K, as the person who is helping with the training plan feels it is possible, as long as I am realistic of my goals. I am feeling strong so far, so keep your fingers crossed!