Every stranger contains memories you could never completely collect.

Each person walking past is carrying decades of experience you will never have access to: rooms they remember, people they lost, a childhood as detailed as yours. This is entirely obvious and almost never actually felt, because the mind renders other people as figures in your scene rather than as centers of their own.

Once this week, look at a stranger and let the fact register for a moment. Not sentimentally, just accurately. It tends to change how you speak to people for the next hour, and it costs nothing beyond a few seconds of deliberate attention.