OK, you don't murder. Is that because of man's law or God's law?
Do you steal?
There are consequences to sin. We don't sin because we don't want to reap the whirlwind of our actions.
Christians don't sin because they are indwelt with the Holy Spirit. The Holy Spirit helps them to live righteous lives. However, they only have the first fruits of the Spirit, which is not that much help, Romans 8:23.