Flat Surfaces

I have this annoying habit that if there is a flat surface somewhere, I will pile stuff on it. For example, my dining room table hasn't been used for dining very often. We have a rollaway bed that belonged to my grandmother out here in the living room/dining room/office area and it's open right now, so guess what? I pile stuff on it. It's an annoying habit that I have tried for years to break (and at least according to my youngest daughter, I've passed it down to at least her). 

​What's your annoying habit?