I went into psychiatry, so I suppose you could call it one big reaction formation. 
Telling my story would feel like hijacking the thread (but can an OP hijack his own thread? Somehow it doesn’t feel like “my” thread anymore since 12 years has passed) and it’s too complicated for me to get out all at once anyway. I will say that I certainly don’t see the world the way I did back then, though I wish I did, but the incongruity between seeing the world that way and the way the world really is was making me unhappy.
I think I realized this at some level, and what I was going for by going to medical school was a “fake-it-till-you-make-it” approach toward becoming a more high-achieving person. I mentioned in the OP that I was labeled a “gifted child” in elementary school. Many of the same cohort of my classmates went on to Ivy League schools, or Duke, Stanford, etc., and became doctors, lawyers, and businessmen. I wanted to prove I could do the same thing.
There was also the female factor. I had a foolish crush on a girl, and I wanted to impress her. I thought pursuing medicine might do it. She did date me for a while, but broke up with me before I even applied to medical school. I kept going with it partially because I thought I’d meet other women who’d be impressed by it, and thought I’d be Mr. Suburban Dad by now. Yeah, that didn’t work.
What I wanted out of life when I posted the OP… due to being a shy, timid kid, and a contemplative dreamer, I had developed the idea sometime in adolescence that the meaning of life was to be found in thinking like a traditionalistic Christian British literary intellectual, along the lines of J.R.R. Tolkein, G.K. Chesterton, and C.S. Lewis. What I would have liked if I had not had to work was sort of to establish my own little world where I drank in the Great Books of Western Civilization, and where nothing in life ever changed. (Think of Tolkein’s Hobbits: they lived happily in the Shire, basically just hanging out, tending their gardens, and smoking pipes.) I now realize that wouldn’t have been possible.
I did find it difficult to be motivated in medical school, though I made it through. Honestly, part of the reason I chose psychiatry is that it’s probably the field in which you least have to know all that anatomy, physiology, etc. that formed the basis of our classroom years in medical school. Am I happy with it? Content, perhaps. I think of myself like the lady in the short story “The Necklace” by Guy de Maupassant. Content, perhaps, but it’s a contentedness reached only through a long, arduous process I’ve realized in retrospect I didn’t need to go through to achieve it.