Kind of a long story, so I'll try to make it as short as possible and I'll be abstract, for my own safety and privacy.
This summer I had to learn something completely new and I had the chance to do it with a wonderful man, with whom I also fell in love, I guess, considering how I still feel about him, although we finished classes a few weeks ago and reminiscing how I felt and behave when I was around him daily. There's no chance or anything else for a relationship, he's married and much older than me (20 years) and I'm just not the type to do things like this, if you know what I mean. What I would really want to, though, is to remain as close friends as possible with him, because when I was around him, talking and learning, I felt like never before in my life, even physical aches passed without medication, just with his presence! I miss him a lot, too much to tell, but he's a very busy man, with lots of stuff to do and he always has other and other students: for each former one that he finishes with, there is a new one. I just want to be alone with him again and to talk like we used to, but I have like mental blockages when I get to see him and anyway, there are always other persons around and I can't say a thing. It would make me so much good if I could just chat with him, but again, what can I tell him, how and when, 'cause he's always very busy and I'm afraid not to sound desperate or begging or God knows what else.
I don't want to let it go, I want to maintain kind of a special friendship with him, but would that be possible, and how in the world?! I'm burning on in the inside and nothing comes out on my mouth 'cause I can't seem to find a moment when he's not occupied or something else...
There would be much more to say, but I hope you got my issue. You can ask questions for details, if you need them.

P.S: Regarding the part where I said "he's a very busy man, with lots of stuff to do and he always has other and other students: for each former one that he finishes with, there is a new one", I would think "why not keep in touch with some of them, right? There isn't a necessity to just pass from one to another and then...nothing." We got on with each other very well and I know he's fond of me because I was a good student and he can clearly see the results of his work on me...But I need a little bit more than just "Hello, how do you do? Fine, you? etc...", 'cause that's what I get now...