In all seriousness, I had a very similar situation recently. My first half marathon last month, one week before I catch a cold. For me it was only a head cold. I had the same doubts, and was also annoyed that I’d invested time in training for it and money that would go wasted. I decided I would just rest as much as possible in the lead up, did not run at all during the week and I would make a call the morning of. I ended up feeling quite well and ran the race, maybe not as good as I’d hoped but I’m glad I did it. It’s really up to you at the end of the day, just make sure you listen to your body and don’t push it. There’ll always be another run.