What is nice is not "being drunk", but "becoming less sober". That is, it's the rate-of-change that's rewarding, while the absolute level is
punishing.

So one is always grasping after the (rather pleasant sensation) of the process of transition from sobriety to a bit drunk.

Or, maximise \int ( M . \delta A / \delta t - N . A ) dt
(I think). I suspect N gets larger as you get older, and M gets smaller as you get more acclimatised ...