Paul offers two principles, freedom and faith, at the same time conflicting and complementary. "One person believes he may eat anything" - freedom, for "I know and am persuaded in the Lord Jesus that nothing is unclean in itself" (Romans 14:2, 14). "But it is unclean for anyone who thinks it unclean" - faith, or lack thereof, for "whoever has doubts is condemned if he eats, because the eating is not from faith" (Romans 14:14, 23).
The ones who Paul describes as "weak in faith" (Romans 14:1) are strong in self-control, but lack freedom. Their restriction on diets and days betrays their Jewish heritage. Food was designated clean or unclean, and feasts and fasts filled the Hebrew calendar. Though followers of Christ, it is hard to let go of the past, so Paul warns them against judging the Gentiles who knew of no restrictions. At the same time, to the Gentiles he warns, you do not have to eat bacon just because you can, "for if your brother is grieved by what you eat, you are no longer walking in love" (Romans 14:15). The one who enjoys freedom harms the one who lacks faith by flaunting his freedom before him.
Martin Luther put it like this, "A Christian man is the most free lord of all, and subject to none. A Christian man is the most dutiful servant of all, and subject to every one"; which is to say, be like Jesus Christ, King of kings and servant to all.
Father, use me to show You off, to help bring others to You and back to You. May I be careful about my influence, that I will not lead others astray or away. Give me an undivided heart, a life that reflects Your character, and a deep love for others.