The quote captures the intense feelings of isolation that can arise when witnessing two people deeply in love, particularly when you're alone in their presence. It conveys a sense of being an outsider, watching the connection between the couple grow while feeling increasingly detached and diminutive. The imagery of an express train moving away from a vibrant city symbolizes the loneliness that can accompany feelings of exclusion as you see others experience joy that feels unattainable.

This metaphor of distance underscores the emotional turmoil of longing for connection while feeling abandoned. The more intimate the couple becomes, the more pronounced the sense of loneliness and despair for the observer. This experience resonates with anyone who has felt sidelined in a situation where love and connection flourish for others while they are left feeling like they are fading away.