Leonard Cohen said this quote

This is the most challenging activity that humans get into, which is love. You know, where we have the sense that we can’t live without love. That life has very little meaning without love. So we’re invited into this arena which is a very dangerous arena, where the possibilities of humiliation and failure are ample. So there’s no fixed lesson that one can learn, because the heart is always opening and closing, it’s always softening and hardening. We’re always experiencing joy or sadness. But there are lots of people who’ve closed down. And there are times in one’s life when one has to close down just to regroup.