I'm not addicted to Diplomacy....just the internet. Which happens to house diplomacy.
From what advice I teenager can give, I'd just say this-
-Stop yourself from playing at work with punishment for each time you do it, by say, I dunno. For each week you manage not to play at work, give yourself a night out, or something you normally don't get. Do the same for home, but limiting yourself to say, 1 hour of diplomacy a day. Keep a timer. Click it every time you log on.
-Finish your games, then take a week long trip somewhere nice. Like Hawaii, or Vancouver, somewhere where you won't have internet.
-Treat it like an alcohol addiction....sign up for an inpatient treatment, and see how that goes.
Hope all goes well.