“Shall we sin because we are not under law but under grace? Certainly not!” (Romans 6:15)
Grace is by no means a license to sin or even to flirt with sin. Grace is God granting us the ability to be conformed to the image of His Son, and empowering us to do so. We are freed from sin, not free to sin. Sin no longer has dominion over us as it did under the law.
We were and are unable to keep the law. Therefore, God sent His Son, born of a woman, to free us from sin and the penalty of it. We do not deserve this freedom on our own merit, but on the merit of Christ. He paid the price we owe.
What then should keep us from sinning? I know of nothing higher than the love of God. If God loved me enough to send His Son to pay for my sins, how could I violate that kind of love? Furthermore, every time I sin, that sin goes to Calvary. Every time I sin, I add to the pain and suffering of the cross. We must never forget - when Christ was on the cross we were on His mind.