Depression.

There's  a demon in everyone’s life and you can not defeat him.

Even if you’re struggle against him, he will always fighting back harder against you. He lives when you live; He leaves when you leave, he stays where you stay. He walks with you, he is inside you, and that daemon is called depression.

To challenge a demon who doesn’t die, a so powerful enemy, you will fight a long battle, in your life, during your entire life; A fight where you can't be average, good or ordinary. You  have to be someone extraordinary. Here, on this battlefield, some will almost close to win, some don’t ,  and some, never will.