What makes this line memorable isn't the goodbye itself, but the defiant certainty behind it—a promise rather than a farewell. The Terminator speaks as if returning is inevitable, that his mission transcends death itself, which transforms a simple parting into an assertion of unstoppable purpose. We recognize that same quality in people who pursue difficult goals: the ones who don't say "if" but "when," who treat temporary setbacks as merely interruptions in a larger trajectory. That psychological shift—speaking with the confidence of someone who has already won—often becomes self-fulfilling.