Why must Christians trust in God's grace rather than their own works?

The doctrine of sovereign grace emphasizes that human effort cannot earn salvation, as indicated in the sermon through the vivid analogy of a lifeguard rescuing someone who is drowning. Just as a lifeguard intervenes to save a person who is unable to save themselves, our salvation is entirely dependent on God’s initiative and grace. Ephesians 2:8-9 reinforces this truth by stating that it is by grace we have been saved, through faith, and this not from ourselves; it is the gift of God—not by works, so that no one can boast. This doctrine ensures that believers recognize their inability to merit God's favor and their complete dependence on Christ's redemptive work, leading to humility and gratitude.