I do teach English as a Foreign language, I used to teach computer programming (at a beginner level), and sometimes I daydream about teaching math according to principles from the essay A Mathematician’s Lament by Paul Lockhart, but I am unlikely to be given the leeway to try.

Mine was just all repeated digits of whatever hour. 1:11, 2:22, 3:33, 4:44, 5:55, 11:11 all “counted” in my mind when I was entering university, and it happened so freaking often it was really weirding me out. It seemed like anytime I glanced at a clock without other intention, it would be one of those times. There were probably times I looked at a clock normally, but of course confirmation bias reinforces things. But it really did seem far more often than you’d expect. My bet is that my inner clock was prompting me to look at those times because I got an adreneline or dopamine or something spike, so my subconscious got trained into finding it.