My favorite exchange on the topic from "Matter" by Iain M. Banks where one character explains their argument, based on morality, for why he believes they are living in the base layer of reality and not a simulation:
Xide Hyrlis: "War, famine, disease, genocide. Death, in a million different forms, often painful and protracted for the poor individual wretches involved. What god would so arrange the universe to predispose its creations to experience such suffering, or be the cause of it in others? What master of simulations or arbitrator of a game would set up the initial conditions to the same pitiless effect? God or programmer, the charge would be the same: that of near-infinitely sadistic cruelty; deliberate, premeditated barbarism on an unspeakably horrific scale."
Choubris Holse: "Of course, your god could just be a bastard."
Obviously had I started from an earlier point, I may have achieved a higher overall peak performance level but that isn't the point I was addressing. Nothing reverses entropy that we know of but that isn't the point either. The point is that saying "you can’t do at 50 what you could do at 25" is patently wrong. I point this out simply because many people have an incorrect perception of their ability to alter their fitness via lifestyle changes.
This is incorrect or at least incorrectly stated with respect to the word "you". I didn't start running regularly until my late 40's and I loathed nearly every step for the first year but my fitness and enjoyment levels slowly improved especially after discovering trail running. I started participating in ultra trail races after a couple years and found a wonderful community of people enjoying an activity all around me I didn't even know existed. Now, 10 years later, I'm the fittest I've ever been and far more fit than the vast majority of 25 year olds.
Am I going to win races against people half my age who are in peak fitness for their age group? No, of course not. But I can physically do far more at 57 than what I could do at 25 with respect to running. Many people can alter the course of their health trajectories at nearly any age but it requires consistent effort and often ignoring the messages of vested societal interests telling them otherwise.
Xide Hyrlis: "War, famine, disease, genocide. Death, in a million different forms, often painful and protracted for the poor individual wretches involved. What god would so arrange the universe to predispose its creations to experience such suffering, or be the cause of it in others? What master of simulations or arbitrator of a game would set up the initial conditions to the same pitiless effect? God or programmer, the charge would be the same: that of near-infinitely sadistic cruelty; deliberate, premeditated barbarism on an unspeakably horrific scale."
Choubris Holse: "Of course, your god could just be a bastard."