Watching the ageing process is scary - at least to me.
One of the best photos I missed just a few years ago: I'm sitting in a restaurant, camera on the table, and walking up the aisle towards me is a very young girl followed by her mom and followed by her grandmother. Their facial similarities were obvious and it was like looking at the progression of time. By the time I'd realized it, they'd passed me. I'd've had to have spotted them a few seconds earlier and grabbed the camera.