I'm massively busy just now and on the train yesterday I was going through everything in my head, sort of a planning conversation with myself. A woman opposite asked if I was ok and when I asked why she said I was nodding my head a lot. Clearly answering myself in my head! We laughed about it and a woman across the aisle said "when you get to our age you start talking to yourself." I asked what her age was and she said 64.
I'm 42.