The moment you became a Christian, a spiritual war began. This battle is not between flesh and blood. It is a spiritual battle with a very real devil. “For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age, against spiritual hosts of wickedness in the heavenly places” (Ephesians 6:12).
When Paul wrote that, he was describing a life-and-death, mortal hand-to-hand combat. While it is true that your eternal destiny changes, you pass from darkness to light, you find new purpose and meaning in life, and Heaven rejoices once you accept Jesus Christ into your heart and life, something else takes place: a spiritual war begins. It has been said, “Conversion makes our hearts a battlefield.”
The believer may be known by his inward warfare as much as by his inward peace. Many Christians do not understand this dynamic of the Christian life. They think that they are set free from the power and ensuing vices that sin brings. They think they are free to just go their own way and do whatever they want to do.
But we are not set free to merely enjoy ourselves. We are set free to do battle and engage in the fight, to overcome in our own lives, and to become channels by which others are set free.
Martin Luther described this battle well in his hymn, “A Mighty Fortress Is Our God”: “For still our ancient foe, doth seek to work us woe; his craft and power are great, and armed with cruel hate, on earth is not his equal.”
Before you came to Christ, the devil wanted to stop you. Once you heard the message of salvation, Satan wanted to take away the Word that was sown in your heart (Mark 4:15). If he was unsuccessful in those attempts, he will next try to entrap you in some kind of sin.