Approaching meditation like exercise is a great analogy. Especially when it can be frustrating and you loose sight that your reaction to the frustration is exactly why you’re meditating in the first place.
I believe it’s vital in meditation to have some sort of measurement of your progress, as you do when exercising, to help keep your focus when facing difficulties. My own practice seems to vary wildly from “great concentration” to “horribly distracted”, and it’s so difficult not to fall into the trap of thinking that “great concentration” is the goal instead the objectivity to whatever state my meditation practice is in. I find that small metrics like, “how long have I meditated today” make a huge difference.