Advice – How do I recover from the breakup of the only healthy relationship I’ve ever had?

I met someone about two months ago who was only going to be in town temporarily before he moves away. In those past two months, I had just the best time with the most respectful and kind person I’ve ever had a chance to connect with. Now that he has moved away, my heart yearns and aches for him. How can I move on? What if he was the one?