Furthermore, from this it is not so very difficult to conclude what it means to train oneself in godliness. It means to: acknowledge one’s sin from God’s Law, seek forgiveness for same from God the Lord and, in true repentance, seek in steadfast faith to cling to Christ and, as a result, produce righteous fruits of repentance (Mat. 3:8), to be fruitful in good works (Col. 1:10), to be zealous in good works (Tit. 2:14), to abstain from evil and do good (Psa. 34:15), to abide in godly living (Gen. 5:22), to serve God with holiness and righteousness (Luke 1:75), to fear and love God (Sirach 2:10), to walk before God in all good conscience (Acts 23:1), to train oneself to have an imperishable conscience towards everyone (Acts 24:16), to deny ungodly ways and worldly lusts, and live chaste, righteous, and godly lives in this world (Tit. 2:12), to be pious before God and conduct oneself blamelessly in all His commandments (Luke 1:6), to dedicate one’s members to God as weapons of righteousness (Rom. 6:13), in service of righteousness that you may be holy (v. 19). to do the will of God (1 John 2:17), to enter in  upon the way of the Lord (Deu 8:6), to hold to God’s Word (Psa 119:9), to walk blamelessly (Psa. 81:12), to cleanse oneself from the splotches of the flesh and go forth with holiness in the fear of God (2 Cor. 7:1), to be found in the stance of good works (Tit. 3:8 and v.14), to be rich in good works (1 Tim. 6:10). (Schola Pietatus-Volume 1 by Johann Gerhard, Repristination Press, p. 19-20)

From all this, it becomes clearly and indisputably apparent that the following three points are part and parcel of true godliness: First, knowledge of sin from the Law of God and heartfelt regret (contrition) over it. Second, true faith in Christ, through which we obtain forgiveness of sins, righteousness which avails before God, the gift of the Holy Spirit, and eternal life. Third, the new obedience or fruitfulness in good works which occur according to the will of God as revealed in the Word. (Schola Pietatus-Volume 1 by Johann Gerhard, Repristination Press, p. 18-19)

However, after the tragic and lamentable fall into sin, things were regarded much differently, because through them [Adam and Eve], sin came upon the entire world (Rom. 5:12) so that from then on, all mankind were sinners before God (Rom. 3:23), conceived and born in sin (Psa. 51:7), were by nature children of wrath (Eph. 2:3), whose hearts’ desires and strivings were constantly evil from their youth (Gen. 6:5; 8:21). Thus, none could any longer say: My heart is clean and I am purified from my sin (Pro. 20:9). Instead, everyone has to sigh: forgive my debt (Mat. 6:12). For if we say we have not sin, we mislead ourselves, and the truth is not in us (1 John 1:8). Thus, from that time forth, it is of utmost necessity for genuine and God-pleasing godliness that repentance be initiated at all times; that is to say, that from the Law of God, one acknowledge the sin which constantly clings to us (Heb. 12:1), bear heartfelt regret over it and, in true faith, turn to Christ—the sole Throne of grace (Rom. 3:25) and, through Him, seek grace and forgiveness from God the Lord. Out of this, good works and zealous effort in godliness will consequently grow forth as righteous fruits. (Schola Pietatus-Volume 1 by Johann Gerhard, Repristination Press, p. 18)