God is stirred by the remorse and the argument and drops half the sentence. Minimally, it is still partially effective. Cain is not doomed to a fate of endless wandering. Our liturgy prepares us to expect less than everything. Our faith in God is not predicated on miracles.
Many conditions are irreversible and actions have their consequences.
But prayer can keep us from panicking, give us the insight to soften the impact, help us to forge the right attitude. The attitude we take to what befalls us is the last realm of human freedom and dignity. Praying gives us perspective. Like Hagar, we catch sight of something vital obscured by our despair. Lost in the wilderness of Beer-sheba without water, Hagar places her child Yishmael in the shade of a bush to die of thirst.