This is how you do it. Choose a sad song. Preferably a song that brings tears to your eyes unbidden the moment it starts. In my case, it was Yaariyan from Cocktail. I didn't choose it so to speak, it just came on randomly while I was listening to music.
Then you get a baseball bat, and break loose. Break it against the windows, against the door, against the walls, against the mirrors. Line up your favourite possessions and break them to smithereens, one by one, or all together if that's what you want. Take everything that belongs to you and smash it all to pieces. Everything that ever brought a smile to your face, anything that made you happy, break it all apart.
Happiness is a futile emotion. It comes so fleetingly that you wonder if it were ever there. It's that sand castle you built when you were a child with innocent hopes and it all fell apart. Another kid running over it, a wave overcoming and washing it away, a parent telling you to stop making a mess and kicking it over. That's what happens to happiness. When you summon up every ounce of yourself to rebuild it, someone else comes to knock it over.
So pick up that bat, and break it all down. Break it all down before you break again.