system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly does Crystal Meth do to someone?  What's so addicting about it?
gpt
Meth makes you really really happy. More happy than you could ever get without drugs. 

But it also reduces your ability to become happy. It very quickly reaches a point where you *have* to keep using meth, because you can never really feel happy without it.