You downplay the "emotional fling" term in your relationship with your coworker but I suggest you re-read what you said and how you are so prone to accommodating him. There is an emotional attachment there that you seem to be in denial of. It was indeed an emotional affair if you want to be honest with yourself. If it was as casual about this guy and it wasn't anything very intense then neither you or he would be drawn to each other, your attention to him would not matter and you would be moving on much easier.

On the note about your being friends. Clearly it's a bad idea to do so. Your not paying attention to him causing him stress is not your concern at all, your well being and state of mind is all you need to worry about. Moving on, cutting him off and letting him deal with the stress himself might seem hard but it's the best thing to do for you.

It sound slike you have a guy that is trying to understand and support you. Do you really want to jeopardize that by putting this other non-important person (in context of your life) at such a high importance level?