I Should Have Known Better by The Beatles is a song that reflects the excitement and idealism of young love. The narrator expresses a sense of surprise and joy at the feelings of love, while also acknowledging a sense of naivety, indicated by the repeated line 'I should have known better.' The key themes include love, realization, and youthful exuberance. Particularly poignant moments in the song include the lines that capture the moment of falling in love and the recognition of how transformative that experience is. The song's upbeat tempo and harmonica accompaniment contribute to a feeling of playful optimism.