"You cannot protect yourself from sadness without protecting yourself from happiness." - jonathan foer (watercolor by courtney khail)
This may have a completely different meaning to someone else, but to me it simply means you cannot have one without the other. It's human nature to shy away from the difficult, the sad, and the frustrating, but without the uncomfortable moments, you're never truly able to appreciate the beautiful, joy-filled moments. (That's not to say I necessarily welcome the "ugly" though. As some who tends to experience emotions very (very) deeply, I'm constantly looking for the beauty in order to balance out any ugliness I see or experience.)