Going soft before an event?

It seems that in the run up to any big event, I start to feel like I'm coming down with something. Right now, my throat is sore - it's not painful to swallow, just feels like I've rubbed the inside of my throat with a bit of sandpaper - and I'm a bit bunged up. This isn't the first time this has happened; just before the Exmoor Beast I felt like I had a cold as well and was inwardly debating whether I should take part or not. I think it is the body performing some kind of psychological trick on me; my body doesn't want to do the Cheshire Cat!! :-)

I just have a 30 minute ride today - just to check the bike is all well and to keep my legs turning round in circles.