Before I wore a uniform to work (which I hate but it keeps things like this from happening as often) I once wore a completely black outfit-pants, shirt, knee-high stockings-with one navy blue shoe and one black one. Had the exact same pair of shoes in two colors and they were on the closet floor, so I stepped into one blue one and one black one. Didn't notice until the work day was almost over. Did the same thing recently-I brought a change of clothes to work because I was going somewhere afterwards and when I went to change I had one navy blue flip flop and one black one in the bag. Probably the worst thing I ever did getting dressed wasn't about matching or wearing anything inside out, but I think it fits here. I had a new pair of nude flats and wore them to work a couple of days one week. They were my size and should have fit, but were terribly uncomfortable, especially at the top of my foot. After the second time I wore them I took them off during the work day to make sure the size was right since they hurt so much to wear, and noticed that I'd left the cardboard used to shape the shoes inside them, which was probably why they hurt so much. I try to make sure I take everything out of shoes before I wear them now!