That is to say, I would imagine my heart rate speeding up or slowing down and either take shallow or a deeper breaths at different speeds. I remember that I figured it out once when the doctor commented on how high my heart rate was and I slowed it quickly enough that they actually mentioned it. After that I started doing it as a game, which I eventually got bored of as children do.

I do wonder how effective I actually was, as it isn't really something I have thought about for literal years.