Yes, there's some scientific medical stuff going on too, like Andante says. I'm not going to google it right now so I'll preface by saying this is what I remember reading, so of course it may be slightly addled between now and then. But as I recall, an addict's brain reforms to have many more receptors for the specific endorphins released by their drug... a big one for alcohol being GABA... and less for the others. So you kind of have to starve it out for a while before it starts opening up receptors to match more accurately the balance of endorphins you can get naturally.
In my mind I picture a house built to gather rainwater for its pipes going through a drought... takes the homeowner a few months before they give in that this is going to last for a while, so I better go dig a well.
I'm at six months and last night I took an ice skating lesson in a community ice rink and it made me as happy as anything. That would not have been the case a year ago. Sobriety brought back simple pleasures for me.