It never really goes away?

From the moment you finally understand that life is shit, and that you can never be totally free and happy, You can't go back somewhere else. Now that you know life is rotten, there's nothing you can do, you can't forget. We just have to live with it until the end of our days ? Why does it seem like others can live with that on their conscience ? Why don't they all want to die ? I think about my parents and sometimes I really wonder why they are still here when I find their lives so unhappy...That's horrible, I shouldn't be thinking that