In this sermon on John 3:8 identifying “Characteristics of the New Life,” Dr. Martyn Lloyd-Jones speaks of the signs of those who have been born again: Christians who have been saved exhibit more than a conscience that condemns their wickedness but also exhibit new desires to please God and wage war against fleshly desires and evil. He describes the differences between a normal conscience that all humans possess and the new life that is given to every believer. Moreover, he shows that anyone who has new life is consumed not with earthly things but spiritual ones. The new Christian is noticeably different to their old friends, and there is a tension put on these relationships. The new Christian’s friends might notice that the Christian acts differently, speaks differently, and spends time in different ways, all of which often drive a wedge between the two individuals who used to have worldly desires and actions in common. If the listener finds these things to be true of themselves, they are encouraged to ask: “have I been born again?”

http://www.mljtrust.org/sermons/characteristics-of-the-new-life/