For my first MM quote I chose a line from Amy And Roger's Epic Detour:
“Saying good-bye is basically an invitation not to see a person again. It's making it okay for that to be the last conversation you have. So if you don't say it--if you leave the conversation open--it means you'll have to see them again."
I absolutely loved this quote, and agree with it wholeheartedly. I've never liked saying goodbye to anybody, I would rather just say "See you later". So when I read this, it really stuck with me.