Those essential interactions make or break life and work. Relations build up, build down, go sideways. They get forgotten. We cease to nurture them and when we notice we have starved them to death.
Then every once in a while you hit gold and find one of those relations that just thinking about them brings a smile to your face. The ones where you catch up and it feels like you never lost touch. Like if time around it froze. I guess the best way to describe it is just magical.