I imagine a person rescued from drowning is entirely grateful to the lifeguard. Amidst total panic, the drowning individual is incapable of assisting the lifeguard. During the rescue, the lifeguard knows the total helplessness of the drowning person, although the person drowning does not. He flails, he pulls, he tries to drown the lifeguard — all in a mighty self-effort to survive.
Paul says to us, “[God] has rescued us from the domain of darkness.” Yes, Paul reminds — we are no longer drowning in deep darkness. “And [God has] transferred us into the kingdom of the Son He loves.” (Colossians 1:13)
If we are not grateful, then we have failed to fully grasp how quickly drowning occurs, how much we fought the lifeguard, and how utterly lost we were.