The Greek words for joy and grace are related; grace causes joy. In the Christian understanding, nothing brings joy like the good news of what God has done in Christ to bring us salvation. Salvation by grace is “through faith—and this not from yourselves, it is the gift of God—not by works…” (Eph. 2:8–9). God’s grace also brings about qualities of conduct in the believer (2 Cor. 9:8; 12:9; Eph. 4:7). The word grace came to be used as a kind of prayer (“grace to you”) in Christian greetings at the beginning and end of some of the New Testament letters (2 Cor. 1:2; 13:14).
The Shaw Pocket Bible Handbook, Walter A. Elwell, Editor, (Harold Shaw Publ., Wheaton , IL; 1984), pp. 250-251.