Here is the Stoic Sage Epictetus:
In every affair consider what precedes and follows, and then undertake it. Otherwise you will begin with spirit; but not having thought of the consequences, when some of them appear you will shamefullydesist. "I would conquer at the Olympic games." But consider what precedes and follows, and then, if it is for your advantage, engage in the affair. You must conform to rules, submit to a diet, refrain from dainties; exercise your body, whether you choose it or not, at a stated hour, in heat and cold; you must drink no cold water, nor sometimes even wine. In a word, you must give yourself up to your master, as to a physician. Then, in the combat, you may be thrown into a ditch, dislocate your arm, turn your ankle, swallow dust, be whipped, and, after all, lose the victory.
When you have evaluated all this, if your inclination still holds, then go to war. Otherwise, take notice, you will behave like children who sometimes play like wrestlers, sometimes gladiators, sometimes blow a trumpet, and sometimes act a tragedywhen they have seen and admired these shows. Thus you too will be at one time a wrestler, at another a gladiator, now a philosopher, then an orator; but with your whole soul, nothing at all. Like an ape, you mimic all you see, and one thing after another is sure to please you, but is out of favor as soon as it becomes familiar. For you have never entered upon anything considerately, nor after having viewed the whole matter on all sides, or made any scrutiny into it, but rashly, and with a cold inclination.
Thus some, when they have seen a philosopher and heard a man speaking like Euphrates (though, indeed, who can speak like him?), have a mind to be philosophers too. Consider first, man, what the matter is, and what your own nature is able to bear. If you would be a wrestler, consider your shoulders, your back, your thighs; for different persons are made for different things. Do you think that you can act as you do, and be a philosopher? That you can eat and drink, and be angry and discontented as you are now? You must watch, you must labor, you must get the better of certain appetites, must quit your acquaintance, be despised by your servant, be laughed at by those you meet; come off worse than others in everything, in magistracies, inhonors, in courts of judicature.
When you have considered all these things round, approach, if you please; if, by parting with them, you have a mind to purchase apathy, freedom, and tranquillity. If not, don't come here; don't, like children, be one while a philosopher, then a publican, then an orator, and then one of Caesar's officers. These things are not consistent. You must be one man, either good or bad. You must cultivate either your own ruling faculty or externals, and apply yourself either to things within or without you; that is, be either a philosopher, or one of the vulgar.
Epictetus aims his counsel at anyone who would seek achievements, but there's a lot here to think about as a middle-aged weekend warrior. More on this later, but here's the question I wish to entertain. Is the pursuit of physical excellence, as an adult, valuable? If so, why?