I have done this before. One day a month or so ago I was feeling so negative and for some reason started doubting that I had lost any weight. Now I know rationally that is ridiculous, but I had it worked out in my mind that I had bought a new scale, and that I had lost a bunch of water weight and that maybe I was wearing heavier clothes before -- all that baloney. So I thought -- I know, I'll go put on my jeans that fit me when I started. I had pushed these to the back of the closet because they were too big, so I dug them out and thought they would be lose and it would calm me down. Well, they fit. Of course this confirmed that I was right and this was too good to be true!

About an hour later I was still going around berating myself and then suddenly realized -- these are not my big jeans! I ran to the bathroom and pulled them down and realized that they were another pair I had been saving that were too small!! They looked just like the others (button-fly) and here I was feeling depressed and doubting myself all day when I should have been celebrating. I put on my old jeans (the ones I thought I had on) and they almost fell off completely buttoned.

I've not done that again since then. But it does go to show how your mind can play tricks on you.