"How do u keep the 1 u love?" - While I no the answer, could I get some explanation?

Question

I was watching the last episode of "Northern Exposure" w/ Rob Morrow where Adam Arkin played the gatekeeper. U'no, answer the riddle correctly & u can X the bridge. The riddle was "How do you keep the one you love?" Joel Fleischmann (Morrow) answered, "You don't." He than explained y not but that went over my head. So, if you've herd this riddle b4, well, y is it u don't hold on 2 the one you love?

Answer 1

you don't hold on because your not supposed to because if it loves you there's no reason for you to hold it against its will because it will choose to stay by its self  "if you love something set it free if it returns it was meant to be."  

Answer 2

easy the saying goes if u love someone you will let them go

Answer 3

because they well always come back to you if it is meant to be