This One by Paul McCartney is a heartfelt exploration of regret, love, and the passage of time. The song reflects on past mistakes and the realization of missed opportunities to express love and appreciation to someone significant. Key themes include reconciliation, the importance of cherishing moments, and the desire to make amends. Poignant moments in the song include the repeated refrain 'Did I ever touch you on the cheek, say that you were mine' which underscores the feelings of longing and remorse for not expressing love more openly.