Regularly fall foul of the saying goodbye to someone, then realising you’re both heading in the same direction.
Then as you walk together you wonder how far you’ll be going in the same direction. If it’s too short, then it’s not worth starting a new thread of conversation, but if it’s too long, then perhaps a more substantial conversation starter would be worth going into. Not that it matters, of course, because by that point you’ve mentally checked out from the social engagement, your mind has moved on. Neither of you knows how to nor really wants to say anything more.
You end up just walking in silence. All the goodwill and positive memories of your time together melting away in front of you as this will be the only thing about your time that you’ll remember.
Then you say goodbye again, perhaps for the last time.