Same here. Also not a well-known science fiction writer. Also that I was ever married (though the divorce would be no surprise).
ETA: I assumed my profession would be in one of the hard sciences, probably either astronomy or biology. Certain lack of specificity there.
My teenage self would not - and could not - understand surfing the internet nor participating in an online forum. Computers did not exist. I am still trying to fully appreciate what it has to offer.
Also, and more significantly, my teenage self has no idea how I was able to deal with the deaths of my children. I had my first at 18.
Like so many others, my teenaged self would be flabbergasted over my entire life. Living here in yet another foreign country, working in a field that grossed me out, enjoying that work, and having the future turn out so much better than he ever imagined. My past self wouldn’t believe that my current self can get up in front of a group of people and talk impromptu without having a nervous attack.
I think it would be the variety of experiences I’ve had, and more importantly, how they shaped the person I became. I didn’t expect, when I was a teen, that I’d find myself in so many different work circumstances, because growing up, we fully expected the safe lifetime employment that’s since been relegated to history. But even though some experiences were unwelcome and unpleasant (layoffs, a year without full-time work, you get the idea), all were valuable. All my experiences made me who I am today–a lot more confident than I was when I was in my teens and a lot less insecure.
Also, I recall all of us in high school being told that we really should decide what we want to be by about age 16, because then we could aim ourselves for it educationally. Some of us did, but most of us were pretty nervous–for all that we tried to project a grown-up persona, we were pretty much still kids, and the thought of having to make a life-ordering decision at age 15 was scary. “What if I choose wrong–I’ll be stuck being a ___ for the rest of my life!” Given this, I think what really would be surprising to my teenage self is the fact that, at age 45, I went back to school. To law school, in fact. Another valuable lesson I wish my teenage self had learned: you need not be slotted into one thing only, and it is never too late to change.
I don’t think my teenage self would’ve been able to comprehend that I’d end up a cubicle jockey, much less one who actually enjoys her work - at the time I was hoping to be a costume designer or something equally creative and artistic (now that I’m older, I realise that kind of life would’ve made me miserable).
She’d probably drop dead of surprise to find out that I’ve earned a reputation for speaking my mind (and get paid for it), even when it means potentially facing some disapproval. I was so shy and insecure back then.
And boy oh boy, would she have been taken aback to find out that I wouldn’t end up married to with the Love of My Life with a few kids to call our own, and end up at 30 in a solid relationship with someone entirely different… with absolutely no plans to get married or have children anytime soon.
I ski *even better * now!
I did that at 27 after goofing around in the liberal arts/humanities. I was going to be a poet! Um except you never see help wanted ads for poets. Or history majors either, unless you want to teach.
Am I totally in love with my job? Not really. But it pays well and I can support my son, and I have a job that is over when I go home. No marking papers, no lesson plans (like most of my history/literature major friends who became teachers) and I do go home every day knowing I made a difference to my patients.
Good luck with nursing, Why Not! The most sucessful students in the class were the adult students. And Nursing School, is harder than nursing.
My adult self can’t imagine that, either. My condolences to you.
The mere fact that I’m so old. Teenaged Sublata really thought she would be young forever.
Also, the cost of living. As a teenager I assumed I’d eventually live in a mansion on a horse farm. Now I count myself lucky to have a small house on three acres … across the street from somebody else’s horse farm. 
Not a whole lot in terms of mental content or lifestyle. That I’m not intense, frustrated, and driven would surprise me and would make me very wary of my modern self.
I asked my wife this question last night and she said “the fact that I’m not working” (she’s taken on the role of SAHM at least until Subkid starts school.
She remembered that in elementary school she had to write an essay about her future self. In it, she wrote that she didn’t want to be an ordinary person: she was going to be an actress, an author or an artist. And if she couldn’t do any of those things, then she was going to marry a foreigner.
So I guess I was her emergency backup plan.
There’s also that I don’t mind being old. That in fact, it’s sometimes pretty nice. (Well, not the aches and pains part, but it has its moments.)
Actually, I don’t think my teenage self would be surprised by much, except that I now wear my hair short, don’t wear all black, drink (a little) alcohol, and can (sort of) decorate.
Oh, and I declared peace with my dad. That would come as a big surprise.
My teenage self would find almost everything about me baffling and sad.
Well, I’m sure teenage me and adult me would have no trouble agreeing on how boring our home town was.
Teenage me probably would find the fact that I lived, work and party in Manhattan pretty unfathomable. For the most part teenage me had just assumed that people went to keg parties and college bars through high school and college and then went out and got jobs and familes and acted like our parents. In fact, teenage me would probably be surprised by the sheer number of infantile morons one finds in the adult world.
My mom is in nursing and she has advanced degrees from Columbia and Yale.