All relationships go bad despite of all the good intentions on both sides. He can say I am the best designer he's worked with. I can say he is the best boss I've had. But the fact of the matter is we tread seeing each other. We have less and less common interest at work. We have drifted apart. What happens in work place is they like you as long as you are necessary.
Many times I vowed to keep in touch with someone. A lot of times I was only saying that. But I did mean it in a few times. It is no use. Despite of all the good intentions, no friendship lasts forever.