When you wake up after a good night’s sleep, your mouth tastes bad and there’s gunk in your eyes. These are toxins that your body expels. Without proper sleep, you wake up grouchy and unable to function well because of poor detoxification. In short, how well you sleep determines your mental health, your physical safety, and your quality of life. Because many people can sleep well on a mattress of the right firmness, you can now buy a mattress with adjustable firmness.