i sometimes get the seasonal change plague, which is basically a head cold from hell and i pretty much take a break from all aerobic stuff for a few days. i find that if i do anything really physical during this time it just totally wastes me, which sucks because if i don't ride or do some kind of exercise for more than a couple days i become a complete basket case.
been drinking lots of OJ this year in an attempt to fend off the beast. so far so good.