What is sadness? where is the sadness from?
I don't know the answers. Even no one can answer. Actually sadness is one kind of feelings. Naturally there are 6 different feelings in human being. Such as Happiness, anger, envy etc. Sadnes is one of them. It comes very naturally.
But when it's come, some people can't control theirself. Some of us are very emotional. They don't know actually how to deal with sadness. During this period they are feeling insecured, lonely and week. And according this feelings they do some massive damage with their life. But after this situation they can understand what has they done.
And then there has nothing to do. So when we feel really bad, we should control ourselves. We should believe that everything will be solved and keep patience till the situation come under control.