I would mainly advice you not to worry too much. Just do what you feel like today, so if you are not feeling well probably the best is to rest. You can make up for it some other day of the week or just completely forget about it. The same goes for tomorrow's run, focus on feeling healthy and you will have plenty of oportunities to make up for any distance that you might have "lost" while not feeling ok.

Self discipline is important when following a training plan, but staying healthy is much more important, so don't overdo it.