1 peter 2: 16 Live as people who are free, not using your freedom as a cover-up for evil, but living as servants of God.
Freedom is often misunderstood. Common wisdom thinks that freedom is being able to do whatever you want to do. Being free is being able to sleep around, get drunk, spend money, bend the truth, live large. But in reality, that's not freedom, that's slavery. If that's how we live then sex, alcohol, money, power or image become the slavemasters and we end up spending all our time, money and effort chasing those things. We are in slavery to them. 

True freedom comes from submission to God, where everything else takes on it's rightful place and we're free to enjoy created things while worshipping the creator.

Freedom and grace in "christian" circles can be used as a cover up for doing evil, as this verse tells us not to do. God's grace is not a licence to sin, knowing that I'll be forgiven. If that's the way we think of God's grace, then we never really understood it in the first place.