...when, in public, you see a plant that looks almost exactly like Tundra Cotton...and you almost go to collect it.
...proud of yourself for having been outside in the shaded sunlight for two hours, you get on Skyrim. You find your character walking out of the thieves guild, remembering that you had taken some Riften bedlam job from Delvin. You go to a place, taking 10-15 minutes to completely steal everything (from valuables to brooms and tankards).... only to realize that everything was free to take, anyway.. Then, you go and clear out the alchemy shop, calculating in your head how much you had stolen. Wondering why your quest isn't completed, you check the journal only to realize that you had taken a numbers job in Markarth.
(it's kind of like waking up early, dress, and get ready to catch the bus for school, and then looking outside and realizing that there was 5 in of snow outside...which, like the journal, had been there the whole time)