I put it off all morning because I hardly got any sleep with a razor blade sore throat last night (which I still have), but I found an article saying a study found that so long as any cold symptoms are from the neck up, then it's okay to go. I have had two days rest so thought I'd give it a go and just stop if I needed to.
The psychology of running is fascinating, it went really, really well and I even felt better afterwards. Yet the other day it seemingly should have been fine and wasn't. Weird!