"Broad is the way, that leadeth to destruction and many there be which go in thereat (Matthew 7:13)." Some of our well meaning evangelical friends have a false assurance of salvation thinking that a momentary recognition of Christ gives them a license to do what they want (i.e. often called easy believism, what theologians call antinomianism). Even Protestant ministers have been aware that many of their own teachers serve up a cheapened gospel that gives a false assurance of salvation:
We Lutherans have gathered like ravens round the carcass of cheap grace, and there we have drunk of the poison which has killed the life of following Christ.... But do we realize that this cheap grace has turned back upon us like a boomerang? The price we are having to pay today in the shape of the collapse of the organized church is only the inevitable consequence of our policy of making grace available to all at too low a cost. (Dietrich Bonhoeffer, The Cost of Discipleship as quoted in Christian History, Vol. X, No. 4, pp. 28-29)
I John 3:9 tells us that the believer will not continue in a pattern of deliberate sin. This means that, if we are true believers, there will always be a change in the way we live our lives.
You can have a true assurance of salvation -- to know that you have been redeemed by the atoning sacrifice of Christ's blood for you. However, a true assurance can never be obtained without committing your life fully and completely to Him. A saving faith is an active faith that bears fruit. There must be a change in the pattern of sin that you live in your life.