you could set your clock by it

Why does it never fail that I ponder a story problem for hours–such as how the ancients knew the world was round and where the hidden weaknesses were in the earth’s tectonic plates–and then figure it out EXACTLY when it’s time to rush off and pick up the kids from school? By the time I spend 45 minutes driving around to two different schools and two different car lines (man, do I hate school car lines!) singing “waving your bladder” and “baking carrot biscuits” I’ll have completely forgotten the answer!