I sometimes get a funny feeling when I leave the office at lunch time. Nothing to do with using cheese past it's use by date for my sandwiches, but its about the habit of leaving the office.
I try to take lunch in with me when I can, sometimes it's a few left-overs, sometimes something more substantial. When its a larger meal I then don't need any top-up from Tesco, but I don't just want to sit at my desk, so I go for a walk. It's then, when leaving the office and hitting fresh, un-conditioned, air that makes me want to buy something.
I think it's the process of leaving the office, so often it is to get something else to eat, or pick up something I need, but it follows the same routine; I leave the office, walk for a bit, buy something, return to office.
I left the other day, stomach full and no need of anything for the house or myself, I just wanted to get out of the office, but I felt the habit of buying something quite a pull. I started thinking of things I could buy; maybe just a chocolate bar, only 50p or so... but my inner Mustachian, or what have you came to the rescue, "you don't need chocolate and there's cereal in the kitchen if you get hungry, that would be better anyway, walk on."
I resisted in the end, I know, I'm a hero! I could try and overplay it, that by eating more I'll be getting fatter and needing to buy new clothes or endangering my health... or that I'll be pushing back when I can retire by spending all that extra money... it's not that dramatic, but I was surprised by the pull of this innocuous but very present habit.
Now I've noted it, I can avoid it by thinking of a specific route to walk, so I leave with a separate purpose.