Songs came from poem, but do you wonder how can a writer wrote all this ideas. Probably the idea didn't come from his mind, but from his heart. That's why many songs are revived today with there new arrangements or versions. Our taste in music change as time goes by but the message of the songs that we want to hear doesn't change. We all have experienced extreme emotions only with different settings or situations. Some of us got broke, some got to an accident and some got a broken heart. All this situations give us extreme emotions. But of course extreme emotions are not all negative feelings, there is also the positive one. If you had met the one, or you just passed your Bar or Board exam, or if you are just simply satisfied with what you have right now.
But if you can notice most of the songs that have been revived or had a different versions mostly are about negative feelings. It's maybe because most writers becomes more creative when they feel extreme negative emotions, especially when they have a broken heart.