I have found in the past that whenever I do some sort of "extreme exercise" it seems that my body goes into water-storage mode. Yesterday I played a racquetball tournament and probably burned 1500 calories and ate sensibly the whole day. So it is tough to step on the scale and it show 2 pounds heavier than yesterday.
I know it's water weight, but it's hard not to be a little bummed. I've got to stick it out the next couple of days to get my body back in balance.