Before you start anything, think about what it will take and what might happen. Then decide. Otherwise you'll start with excitement but quit when things get hard. "I want to win at the Olympics." Fine, but think it through first. If it's worth it, then commit. You'll have to follow strict rules. You'll eat a rigid diet. No treats. You'll train your body at set times whether you feel like it or not, in blazing heat and freezing cold. No cold water. Sometimes no wine at all. You'll hand your life over to a trainer like you would to a doctor. Then in the actual competition, you might get thrown in a ditch, dislocate your arm, twist your ankle, eat dirt, get beaten up, and still lose. Add it all up. If you still want to do it, then go for it.
In every affair consider what precedes and what follows, and then undertake it. Otherwise you will begin with spirit, indeed, careless of the consequences, and when these are developed, you will shamefully desist. "I would conquer at the Olympic Games." But consider what precedes and what follows, and then, if it be 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, and sometimes no wine—in a word, you must give yourself up to your trainer as to a physician. Then, in the combat, you may be thrown into a ditch, dislocate your arm, turn your ankle, swallow an abundance of dust, receive stripes [for negligence], and, after all, lose the victory. When you have reckoned up all this, if your inclination still holds, set about the combat.