The thing about meth is that when you're high, you're on cloud nine. You're untouchable. Nothing could go wrong. Then you need it more, but just to feel "normal". Then you need even more just to stay awake. And when you finally get clean, nothing is quite the same anymore. You aren't as happy as you used to be. The zombie-esque state you see former addicts in is because their dopamine receptors are shot. And that's why I rarely smile nowadays.