The song 'The Biggest Lie' by Elliott Smith delves into themes of self-deception, emotional pain, and the complexity of personal relationships. Smith's poignant lyrics explore the notion of lying to oneself and others about the reality of one's emotional state. The key themes include introspection, vulnerability, and the struggle to come to terms with personal truths versus the facades we often present to the world. Particularly poignant moments in the song include the lines where Smith reflects on regret and resignation, highlighting the emotional turmoil and the internal conflict of accepting one's own weaknesses and mistakes.