Have you ever encountered someone from your past, who you used to be very close to (or perhaps WANTED to be close to) and you see that they are now very close to someone else?
You see the joy that they now have because of it.
And it's refreshing, in a way.
It's like an affirmation that you letting them go really was the right decision, because now they have this joy with someone else that they couldn't have with you.
And that's a really cool thing.