start by raising temps, give it a month or two.
if it's still not carbonated, you might need to add fresh yeast. i would recommend champagne yeast - make a slurry, wait 20 mins and then start slowly adding some of the beer to the slurry to acclimatize the yeast to the high-alcohol environment, then uncap a bottle, add a few drops via an eyedropper, and re-cap with a new cap. is the beer not carbonating enough, or is it completely flat? if it's perfectly flat, then you should still have enough initial priming sugar left in there. if it's started to carb a little, then you might consider adding a very small amount of sugar to the slurry to replace the already-consumed sugar.
BTW, you didn't "let the belgian yeast go at it for too long". the yeast was going to do whatever it was going to do. you can't stop it, short of killing it (then how would you carbonate?). it's better for the yeast to have munched down in the bucket/carboy as opposed to in the bottle. had you bottled before the yeast finished attenuating, you could have had bottle bombs.