My personal rule of thumb is that nothing works as efficiently as you age so don’t expect the same results as a 30 year old.
I’ve come to a somewhat different conclusion, but there is obviously some truth in what you say.
I am convinced that if we continue to treat our bodies like they were thirty, getting a lot of exercise and eating well, we’ll remain a lot closer to it, than if we accept the inevitable and surrender to it.
Go out and run folks. Go out and run those patterns you did in football.
Do your exercises. Lift weights. Do pushups and situps. Exercise your mind.
Live life to the fullest. Think young. You can be at any age.