"Flee from sexual immorality. All other sins a man commits are outside his body, but he who sins sexually sins against his own body. Do you not know that your body is a temple of the Holy Spirit, who is in you, whom you received from God?" NIV translation
We defile the temple of God (our bodies) when we commit sexual sin. Because of the Holy Spirit that lives in us, we are constantly being made holy (set apart for God's use) and, so, sexual sin has no place in our lives.
"You are not your own; you were bought at a price. Therefore honor God with your body." NIV translation
Although it is not popular to say, Jesus bought us with His blood. Since He bought us, we are no longer our own but belong to Him and so we want to honor Him. When we come to Christ, it is asking Him to be both Lord and Savior.