Murphy's Law of Intersections

"You can 'watch 'n' observe' as carefully as you please while driving and you will still miss your turn-off, and so no amount of continued 'Oh, I'm sure it's just around the next curve" tootling further down the road will bring you to it. But if you do actually decide to turn around and go back to see if you did inadvertently pass your desired intersection, it will of course NOT be 'back there', and you will subsequently find out that you'd been within just a few hundred yards of it at the point when you'd turned around, and so you simply wasted gas and time by backtracking; it had indeed been 'just around the next corner', and so you'd have reached it the first time if you simply hadn't been so gol-durned impatient."

I missed my turn-off during a road-trip because I was carefully watching out for traffic and thus never noticed the side-road I wanted --- classic case of Murphy's Law of Intersections!