If you have an adictive personality it's quite possible to get addicted to endorphines in a bad way which is what that gets released when we experience pain. But since we're all "addicted" to endorphines naturally, it's probably a bit too harsh talking about addiction here. "Liking it very much" I'd say is probably a better term.

Our brains are a veritable drug factory quite naturally and I can imagine it being easy to over-do it if we find a handy way to release a lot at once

edit: My point is that the state of happiness is having these chemicals released, and if we use the term addiction, which is asociated with something negative then I think we've lost track of what it all is about. I'm not going to make any claims as to what the purpose/meaning of life is, but while I'm figuring it out, having fun, enjoying life and aiming for happiness I think is the best goal I can come up with.