I've been reading about cortisol, a hormone that our bodies produce in order to cope with stress (Wikipedia). I am not a doctor, so I just gathered some facts from the Internet.
Cortisol is necessary for our survival. However, when we undergo great amounts of stress, this same hormone can supress our immune system, because it prioritises dealing with whatever it considers to be a threat to us first (that is, the cause of stress). So if, for example, someone loses their job, their bodies will see this as a threat to survival and produce cortisol. If that same someone happens to get a cold virus at the same time, this gets second priority and is not dealt with until the primary threat is over. Simply put, our bodies are weakened when we're stressed, leaving us vulnerable to illness (http://www.richardweinsteindc.com/disorders.htm).
Exercise can help decrease the amount of cortisol (About.com). Excessive exercise can however be stressful to the body, causing cortisol to increase (http://deepfitness.com/741/Cortisol-and-Overtraining.aspx).
Running 49 km in the snow might be a balsam for the mind, but it's not as kind to the body. It IS a stress factor, at least when you're not a weathered ultrarunner. Add that to a prolonged period of intense stress at work, and it's no wonder I'm sick yet again. It's pretty ironic that the thing that helps me cope with stress the most tipped the scales over, so that I got sick again.
Zen, man. Olympus, 2009.
What I need now is a long vacation in the sun, but that's not going to happen any time soon. So second best is rest and fun, relaxing things to do. I need to eat good, nutritious food. Go out with friends. Laugh. Play with the cats. Take up yoga. Go for a walk in the woods. Take care of my body, because it's the only one I've got.