A little optimism never hurt anyone. It's his birthday, so why should he have a dark cloud over his head? He will go through his own recovery on his terms, but having a positive attitude that it will get better, is something that will help him go further in his recovery. He probably already knows deep down that recovery isn't a soothing cup of international coffee but is trying to keep a positive attitude. The best thing you can do is to stand by him in good times and in bad, just as you promised when you first got married.
“If a man wishes to be sure of the road he treads on, he must close his eyes and walk in the dark.”
- Saint John of the Cross