The year before last Sakuracon I was pretty sick on day 0 so I started taking some Zicam dissolve tablets. Only according to the box I had to take them every 6-8 hours, for several days- which was the length of the cold anyway- and that consumed the entire package. I was still sick with a stuffy nose and watery eyes and mildly sore throat, and had the taste stuck on my tongue all weekend. The symptoms would go away for about 4 hours after taking the medicine, but for another 2 I was just miserable, and waking up in the mornings was bad too until I got the medicine in me.
Oddly enough, last Sakuracon, I was so sick that I was unable to eat. I was running around, but unable to keep any food down and had to choke down a lot of water, and force myself to eat an entire bagel over the course of just one day. It was pretty bad. Upon arriving home, I found out I had a bad temperature and forced myself to eat some bananas, and felt fine after a few hours.
Being sick does weird things, but I'd suggest if nothing less, to at least drink a lot of water if you feel or are sick. I've started carrying generic antihistamine with me for the sniffles I might get, and will be loaded up on a lot of multi-vitamins (strong in the B and D), so hopefully this next Sakura I won't be sick. I had a lot of multi-vitamins at Kumori and had a half cup of peanuts each morning, and barely got any kind of sickness.