Help re-tame a bearded dragon?

I have a bearded dragon, he was nice and tame when we got him fine being handled. Then my girl friend had to get a puppy, which was a hand full and required a lot of attention and thus the beardie was left not getting nearly enough attention. Now he is an angry little lizard, does not want to be handled or even have me near his cage. Gets all black beard and snappy I like him and would like for him to be nice and tame again so he could be out and handled, hanging on my shoulder watching tv and or roaming the couch and window sill with out striking at us does anyone have tips to re-tame a bearded dragon?