Ditto on regretting not starting sooner.
I've done varying amount of exercise throughout life, but really dedicating myself to whole body weight-training/yoga/core-and-balance over a period of about a year has fundamentally changed my life in countless ways.
I wouldn't even say you understand it once you start. I think understanding requires going for a while without injury, passing your noob gains phase, hitting a plateau and seeing results again.
Especially for someone like me into "depth" in strategy games... you realize that the only limits are genetic & mental and the "skill curve" is infinite. Putting effort into training, eating or resting has largely supplanted my desire to play video games.
NB: I had previously done a Starting Strength program a decade ago with a not-so-great coach. Coach was a dickhead and didn't discourage me from some really bad training habits that led me to get injured. Injury led to depression, weight gain and not getting back to training for a decade. Maybe that's on me but it's a serious regret and the approach I took to training this time around made all of the difference.