The apostle takes his metaphor from athletics. He advises Timothy that if he is striving to win in his ministry, he will not be crowned unless he disciplines himself to follow the rules.
In games (whether cards, croquet in the backyard, basketball, or whatever), we are often confronted with the opportunity to bend or to break the rules. The player must discipline himself or face the penalties and maybe even find himself disqualified. If a player breaks the rules in football, he receives a 5-yard, 10-yard, or 15-yard penalty. In some games, the rule-breaker just gets thrown right out! The athlete, then, must discipline himself.
Paul uses this in regard to members of God’s church. If we desire to be crowned, we have to strive within the rules. We have to discipline ourselves. In Timothy’s case, the rules are scattered throughout Paul’s epistle to him. In terms of the Sabbath and the annual feast days, they are the only days in the entire Bible that God designates as “holy.” They are part of “the rules.”
God never gives His approval to any day of the week save Sunday, which is set apart for our worship of Him. He never gives His approval to Halloween , Christmas , Easter , and all of the other manmade holidays. There is nothing wrong with manmade holidays as long as we do not place God’s approval on those He has not authorized. We have to strive for mastery within the rules and use them in the proper way to be awarded with ultimate prize.