When I would send my kids out the door to school, I would often say 'Make good friends and keep good friends'. It became my sign off for the morning. I love the simplicity of it and it encapsulates exactly what a successful day is like. You go about your business with the idea in mind that you are looking to care for someone. You don't know when that will be, or what form it will take. It might not be something you even realize is 'care'. You might just laugh heartily with someone over something silly. But to that person, the laughing was such good medicine, so unexpected, that you became a friend without even knowing it. You might listen to a fear that is just one sentence in a long monolog, but you pick up on it and reassure the person later in the day.
Friendship is about awareness and attention for another. The new friends bring that excitement that makes us young, nerves, telling stories, allowing yourself to be seen anew, perhaps reinventing yourself just a little bit for the new audience.
The old friends give us the comfort and assurance that come from us knowing that they know all about us, they know our flaws, our shortcomings, our eccentricities, and they are still with us, they still find value in us, they still love us.
In both ways, the essential nutrient of friendship is resupplied to our souls.