Common manifestation: I'm upstairs in my bedroom, waiting out the clock until it's time to go downstairs and collect myself for work. "Don't forget that you need to collect a couple items from downstairs before you leave," I tell myself.

Then, thirty seconds later, I march downstairs, do my usual few pre-flight checks, grab my bag and leave. I remember the other items when I'm a block away (and then decide it's too late to go back for them, dithering long enough to miss my bus or train)