In this sermon, Pastor McKinney highlights the importance of regularly remembering our humble beginnings as Christians and the mercy we received from Jesus. He uses Jonah's story to illustrate how forgetting God's mercy can cause our mission to fade, just as Jonah lost sight of his purpose when he became resentful over God's compassion for Nineveh. Pastor McKinney emphasizes that the longer we are Christians, the easier it is to fall into self-righteousness, leading us to focus on our own goodness rather than the grace we've received. He encourages everyone to keep the mercy of God at the forefront of their lives through regularly gathering with the family of God and the observance of the Lord's Supper.