So here's the story. A friend of mine who's over the years always been a "good drinker"(meaning he was always happy when he drank and didn't cause trouble) suddenly seems to have become a bad one. Just today while drinking with him I had to physically separate him from his father after he had a fight with him and pulled out a knife. After that we went elsewhere and got in an argument with some pscyho who eventually came back with a friend and two baseball bats which he and his friend used on us(he got it worse than I did but we both went to the ER after calling the cops). This came a week after I intercepted a punch meant for him while trying to seperate him from two other guys in another fight. Suffice to say I'm now quite angry at him and reluctant to drink with him again. But how did that happen? I've been drinking with him for the last three years and he never once caused any real problems. He drinks about as much as he always has(not every day and not very much-he's really a bit of a lightweight, at least in our company) so I don't think that's the problem.The only reason I can think of is that we've been slamming drinks a bit more(usually a pint of beer-0,5l or the same amount of wine). But we've always done that so I again doubt that's the issue. Please give me some advice so I can enjoy drinking with him again