Jesus is, to put it mildly, a Man of His word. In fact, He is the God-Man of His word. He is the incarnate and eternal Word. Consequently, it is in character for Jesus to say in the Sermon on the Mount: "Say 'Yes' when you mean 'Yes' and 'No' when you mean 'No.' Anything beyond that is from the evil one" (Mt 5:37). Jesus "was not alternately 'yes' and 'no'; He was never anything but 'yes.' Whatever promises God has made have been fulfilled in Him" (2 Cor 1:19-20).
Therefore, when we renew our baptismal promises at Easter Vigil or Easter Sunday Mass, the Lord expects us to mean what we say, that is, to reject Satan and live lives of faith in the Father, the Son, and the Holy Spirit. Moreover, after we pray the creed, Jesus expects us to be men and women of our word and be under His lordship and faithful to His Church forever.
Because Jesus is a Man of His word and is the Word of God, Jesus also expects married couples to be faithful to their wedding promises and priests and religious to fully live their vows.
Jesus will give us the grace to be men and women of our word both in our major commitments and casual conversations. Because He is the Truth (Jn 14:6) and lives in us (see Jn 17:23), we can be true and faithful by His grace. In His Word, be a man or woman of your word.