One excellent book on the topic of godliness is Willem Teellinck’s (d. 1629) The Path of True Godliness. The following lines give a great snapshot of this discussion.
“We must therefore begin to practice [godliness], not in our own strength, which means absolutely nothing, but in the power of our Lord and Savior Jesus Christ, who is the strength of our life and by whom we can do all things. [Here Teellinck quotes Eph. 6.10, Phil. 3.3, 2 Cor. 3.5, and 2. Cor 9.8).”
“Take careful note of this, for surely many a man begins the practice of godliness and then gives up in discouragement and withdraws from his work. Since he began it in his own strength, he makes a mess of things. It’s exactly the same thing as when a little child, in his own strength, wants to build a big castle. It is a fact that our own strength means nothing in the building up of the Christian life. Unless the power of the Almighty comes upon us, we cannot build anything that will last. That is why we call it godliness; it reminds us that without God and his holy help we would never be able to accomplish this work.”
“How the devil tries to keep this fact hidden from the eyes of men! That is why there are found everywhere so many who now and then put on holy airs as if they henceforth want to be godly, but you see after only a short time they have returned to the world, having so very quickly lost interest. This happens because they began in their own strength; therefore, they found their work too much for them and quickly tired of it because they found no more joy in it. Therefore, all students of true godliness who wish to begin this work well and truly wish to bring it to completion must renounce their own strength. They must surrender themselves entirely to the Lord Jesus Christ, who is ‘the Author and Finisher of our faith’ (Heb. 12.2)….”
That’s worth reading a few times for sure. By the way, RHB has Teellinck’s book on sale for $11 right now.