I hear ya. That usually happen to me when I go down to the cellar to something. I get to the bottom of the steps and can't remember what I went down there for. But, since my beer refrigerator is down there, I don't go back upstairs empty handed!
Of course halfway through the beer I remember what I originally needed and head back down hoping I don't forget again. But if I do, I still don't go back upstairs empty handed. ;-) It's a vicious circle I tell ya.