. . . the mature . . . have their powers of discernment trained by constant practice to distinguish good from evil. - Heb 5:14
"The relationship between conduct and character is an intimate one. In the form of repeated actions over time, conduct produces character. That's the teaching of 2 Peter 2:14 and Romans 6:19. But it's also true that character determines actions. What we do, we become; what we are, we do.
Conduct is always feeding character, but character is also always feeding conduct. Paul's experience while shipwrecked on the island of Malta furnishes a good example of this relationship. The islanders built the refugees a fire because of the rain and cold. Luke related in Acts 28 that Paul gathered a pile of brushwood, and, as he put it on the fire, a snake came out of the brushwood and fastened itself on Paul's hand. Under the adverse circumstances of shipwreck, why would Paul have gone about gathering fuel for a fire built and tended by someone else? Why not just stand by the fire and warm himself? Because it was his character to serve (Acts 20:33-35; 1 Thessalonians 2:7-9). He'd learned well the lesson Jesus taught when He washed His disciples' feet. Because it was Paul's character to serve, he gathered the brushwood instinctively.
Because conduct determines character, and character determines conduct, it's vitally important— extremely necessary—that we practice godliness every day. That's why Peter said, "Make every effort to supplement your faith with ... godliness" (2 Peter 1:5-6). There can be no letup in our pursuit of godly character. Every day that we're not practicing godliness we're being conformed to the world of ungodliness around us. Granted, our practice of godliness is imperfect and falls far short of the biblical standard. Nevertheless, let us press on to know Christ and to be like Him."
-- Jerry Bridges