It cannot be done so easily. Your body has a thousand instincts inside trying to preserve itself. Many of these people who try asphyxiating themselves end up

It cannot be done so easily. Your body has a thousand instincts inside trying to preserve itself. Many of these people who try asphyxiating themselves end up ripping the bag even after they go unconscious. And if you fail, you risk long-term brain damage. Trying to kill yourself is like trying to kick a the corner of a concrete wall with your shin as hard as possible. You have to override a lot of self-preservation instincts. It's not like you suddenly become immune to pain, loss, and fear.