With thanks to Grahame Crossing who first pointed out to me the biblical principle of the power of grace.
“Grace” and “mercy” are wonderful themes of Christianity. The two words occasionally appear together in verses of the New Testament (especially in greetings), and the concept of grace has sometimes become confused and conflated with the concept of mercy, but the two are not the same. “Grace” has been described as getting what we don’t deserve (e.g. favour and pardon), and “mercy” has been described as not getting what we do deserve (e.g. punishment and death). Yet grace is more than passively receiving divine favour and pardon.
The Greek word for grace (charis) is used 150+ times in the New Testament. Sometimes its meaning is of “favour” or of “a pleasing, attractive disposition” either of people or of Jesus and God. However, grace is frequently used in the context of power, strength, and ability. For example, it is God’s grace alone that has the power to save (Eph. 2:5ff; Rom. 11:6; Tit. 2:11; 3:5-7).
God’s grace working within us also empowers and enables us to be effective agents of Jesus Christ (cf. Acts 4:33; 6:8; Eph. 3:7-8, Heb 4:16; etc), even when we ourselves are weak (cf. 2 Cor. 12:9-10). Paul knew firsthand that followers of Jesus need grace (i.e. divine power) in order to be effective ministers (Rom. 1:5; 1 Cor. 3:10; 15:10; 2 Cor. 1:12; Gal 2:9; Eph. 3:7-8; Col. 4:6; 2 Tim. 2:1). Thankfully, grace has been made abundantly available to us through Jesus (John 1:16; Rom. 5.15; Eph. 1:6; 4:7; 1 Tim. 1:14).
The Holy Spirit is the one who helps us to carry on the ministry of Jesus in the present church age, and is associated with grace, especially the “grace gifts”, or charismata. The Holy Spirit gives his divine gifts, abilities, and manifestations for each of us to use while ministering and serving others (Rom. 12:6ff; 1 Cor 12:1ff; 1 Pet. 4:10).
A faulty understanding of grace can lead to complacency and passivity. God’s grace, however, should motivate, energise, and empower us. It is active and dynamic.
With all this in mind, whenever you come across the word “grace” while reading from the New Testament, try replacing it with “divine power”; it may make better sense.
“The grace—the divine power—of our Lord Jesus be with you!”
(Rom. 16:20; 1 Cor. 16:23; cf. 2 Cor. 13:14)
 Grace (charis) was used in the context of divine favour in the Greek world, and the usual greeting of the Greeks was charein: “to be blessed with divine favour and power.” The New Testament letter writers adapted this convention and typically used charis in their opening greetings. “Grace and peace” (“peace” being the equivalent of the Hebrew shalom) is found in numerous greetings (e.g., Rom. 1:7; 1 Cor. 1:3; 2 Cor. 1:2; Eph. 1:2 1 Pet. 1:2; Rev. 1:4; more here). Grace, peace, as well as mercy, appear together in greetings in 1 Tim. 1:2, 2 Tim. 1:2 and 2 John 1:3. Paul closes his letters to the Galatians, Philippians, and Philemon with the benediction, “The grace of the Lord Jesus Christ be with your spirit” (Gal. 6:18; Phil. 4:23; Phm. 1:25; cf. Rom. 16:20; 1 Cor. 16:23; 2 Cor 13:14; 2 Tim. 4:22).
 Charis has a variety of meanings. Hans Conzelmann (TDNT Vol IX, pp. 359-76) writes that charis basically means something that delights. However, he notes that “In Hellenism charis becomes a fixed term for the ‘favor’ shown by rulers.” He also notes that “Philosophy discusses the grace and the wrath of the gods”. Conzelmann goes on to say, “In a second development, Hellenism stresses the power in charis. This power, which comes from the world above, appears in the divine man and expresses itself in magic.” It seems that Paul, Luke, and other New Testament writers may have borrowed this last usage of charis (i.e. grace is power from above) and adapted it for their own use.
An excellent article about grace with the meaning of “divine favour”, and how the first Christians would have understood this, here.