My math is generally based on song length. So, if I have a 3-minute interval (for example), I say to myself “this interval is going to be over before the song ends”. Or, on a long interval, I look at the playlist and say “ok, I got this… one by Katy Perry, one by Ava Max, and I get to finish the interval with Selena Gomez!”
I know what you’re thinking: whoa, that @Jack_Russell_Racing dude is a weirdo.