Like others, I have some crazy, some epic, some epiphany-type thoughts going through my head when I ride. It happens all the time.
But the minute I catch myself in a stupid mistake as a result of being too involved in thought, that's when I stop, clear my head, and then continue.
My worst problem is rushing. I can't count how many times I've caught myself rushing through the prep to ride, then my mind is still in rush-mode when I leave, and I'll usually make a stupid mistake within a block or two. A quick stop, a few breaths, a mental reset, and I'm good to go.
'13 Yamaha Super Tenere - my dream bike