Don't use your body for sin

“Do not offer the parts of your body to sin, as instruments of wickedness, but rather offer yourselves to God, as those who have been brought from death to life; and offer the parts of your body to Him as instruments of righteousness.” Romans 6:13
Salvation is not just about our spirits changing their final destination. It’s meant to change the way we live, right here, right now. While we are on this planet, we are in our mortal bodies. Although our bodies will decay and pass away, they are still the vessel that we must dwell in for the duration of our earthly lives. We also have the Holy Spirit indwelling us if we are born again, and so our bodies are called the temple of the Holy Spirit (1 Cor. 6:19).
Think of the ways we used to sin before we became Christians. Paul tells us in this verse that our bodies should not be used in those ways any longer. We should use our eyes for reading the Word, not looking at dubious things in magazines or on television and lusting after them. Our mouth should be used for praising God, not telling crude jokes, using bad language, gossipping about other people, etc. Our hands should be used in service for others, not stealing, violence, and so forth.
It is a conscious decision we must make. Our body is unregenerated and prone to sin. But we have the power to bring it in submission to the way God wants us to live.