That "thing"

I wrote this to a close friend over Facebook in one of our typical long conversations…

"Having been at college my first semester, i've realized that there's so much about myself that is a really big question mark of haziness and there are a lot of contradictions within myself that I can't keep living with. I've always grown up with piano, and even though I wrote about it in my college essays and it was my "thing", I don't know or I don't think it's that one thing that I'm truly passionate about. I had to fill out a short bio at the beginning of the year at my research assistant job in the Human Computer Interaction lab, it was a short bio like "hi my name is Jen, I'm a freshman studying Information Systems, etc etc" and the last part we had to answer was "if i had a whole afternoon free, I would…" and I was reading the responses that other people came up with, like "i enjoy hiking and fishing", "i enjoy cooking, listening to rock, and playing the sax in jazz bands", and it wasn't a moment of crisis for me, but i realized I didn't know what I would put. Like people have those things that they could do for hours and not feel the passing of time and just get completely lost in that thing and they find so much joy and satisfaction in it that if they had a whole afternoon free, they could point to that and say "god i would kill to have an afternoon to do that for hours on end and it would make me so happy"
and i want to find that, whatever that thing is. and yeah, my dad was telling me about his coworker who discovered an intense love of astronomy and telescopes when he was in his forties. he bought a telescope for his son, his son never touched it, and so he picked it up and started dabbling with it and the rest is history, he reads books and books about it, goes to conferences and talks about it, and it just brings his life so much excitement, and i think it also makes him a more interesting and distinctive person, it formulates part of his identity. and i want to figure out or find what that thing is, some sort of direction or purpose or excitement in something"

…I wonder how he will respond. How does one respond to something like that?