I've been training for a spring marathon since mid-January, and although I think I started early enough, now I'm fighting off a bad chest cold. This will be my second day without running, and I'm worried about de-conditioning. I'm up to 30 miles a week, and this will be my first full marathon. I know I can't run sick, but this is a huge set-back. Any advice on how to get back on track when I'm over this?