I unintentionally dropped a dress size. I was shopping for a dress to wear to a wedding (always a bridesmaid / attendee / drunken reveler, never a bride) and was disgruntled that nothing fit appropriately. Lo and behold, it turns out I'm one size smaller. In disbelief, I asked the sales clerk if they had recently changed any of the sizes, as several stores have done over the past few years. She says no, and I celebrate.
My celebration was quickly followed by panic that I won't be able to actually maintain this weight until it's time to wear the dress, and now I'm miserably obsessing over my weight.