Moz, all you can do is try to remember the good times you had together. Try not to focus on the argument or any regrets you might have, try to pay your respects in a positive way so that when you remember them you can smile instead of frown. I've had a lot of experience when it comes to this kind of thing so feel free to PM me if you feel you need to talk to someone. The most important thing you can do is take things at your own pace, and also try not to let it ruin your Christmas - it's a good time to remember absent friends in a more positive way. Maybe you could meet up for a drink with some people who knew you both as well as spending time with family and friends.