So me and this guy named Garret have been really close, I would say best friends for about the past year and a half or so. We've always gotten along great, but lately our relationship is deteriorating and I am unsure what to do about it. He is constantly arguing and acting aggressively towards me. Everything I say, even the most innocent statement, he finds a way to contradict. He raises his voice all the time and perpetuates small arguments into huge fights. I feel his behavior stems from his depression right now, because he is very caught up in drugs and spends most of his time either selling or smoking(something he never did when things were good). He also is very lonely, he hasn't had a real girlfriend ever and most girls don't give him the time of day. I feel as though he takes out his aggression and sadness on me because I am closest with him. But I'm starting to get really bothered by it. I feel like I'm losing my best friend, and I am powerless to stop it. I myself have not been perfect, I have done some things to hurt him in the past(involving females -__-)and he probably still holds resentment towards me because of that. I also engage in arguments with him when I probably shouldn't, but I get so frustrated with how he acts that sometimes I can't help it. Any advice on how to make things better?