The Marines have a saying - "Until they are home, no man left behind". In the U.S. Soldier' Creed - "I will never leave a fallen comrade".
We connect to others through friendship, culture, heritage, commonalities, teams, organizations, religion, and the list goes on. Google calls these connections circles; Linkedin has groups; Historically, your primary circle was called a tribe.
Yet these circles are just a small multiplication of self. We are naturally attracted to some people more than to others - they become friends. Each "circle" of connection is seeing yourself. When you meet someone new the conversation volleys about as you attempt to find commonality. How comforting it is when you happen upon a location you both lived, or a person you both know, or an interest you both promote. It is this "dance" that attempts to discover whether you see yourself in the other person.
But even with that commonality, it is the extension of the circle that expands "the self" in ways we can grow. It is our various interconnected circles that remind us of our wholeness - connected not only to each other but to something bigger than the whole.
"Learn to look with an equal eye upon all beings, seeing the one Self in all" - Srimad Bhagavatam
When we understand the circle of connection is everyone and is only one - then the saying becomes:
Until everyone is home, no one is left behind.