It is better to be away from few months and start believing that, time heals almost everything. On an other side, your friend will be start investigating what actually went wrong, or, it may be self analysis of the whole scene. It maybe because of harsh and loud response to your friend, when he was emotionally down. Or it maybe a joke which was taken personally and meaningfully. We need to know that, everybody makes mistake while communication, it maybe because of over excitement or replied when you are mood-off, not able to judge properly. This happens in every life.