I hate the idea of people leaving. Not the usual "Alright I gotta go now, BYEE! :) Talk to you later!" but more like the I-don't-know-if-we'll-be-able-to-meet-again type. Because you never know how things will turn out. Because you don't know when's the next time you're going to see each other. Because the future is really vague without them important people in your life.
Maybe certain bonds will still last, even if they're not there anymore. Maybe things will remain the same, even if they're gone. But everyone knows that, that's not true. Life's clearly not a fairytale anymore. Not everyone's going to be there for everyone just because you "need" them.