Thank you everyone. Especially m1469 and Bernhard. And Motrax.
I am also studying to become a physicist. However, since I have no actual experience in a research environment yet (hopefully next summer), and because I am very distrustful of bureaucracies in general, chances are that I will not indulge my love of pure knowledge (I also thought about math and philosophy - the two most ivory-tower disciplines) by becoming a university professor/researcher. If I do stay in physics, I will look for a job in industry (optics? electronics? materials?) somewhere.
Of course, I am also a pianist. Although I've played for most of my life, it's only recently (after discovering all the great masters of the piano, and meeting my piano teacher at university) that I've really become deeply into it. For the first time, I've felt I had the chance to take my playing SOMEWHERE. Not that I have a wonderful technique or anything - it's just that I have learned how to control my direction more. I don't feel so much like I'm wading into pieces that I don't understand (until I met Ravel

) And I love performing. It's so much fun.
So now I'm not really sure which way I want to go. I am realizing that either way will involve a sacrifice of the other. I'm scared of losing my piano, but at the same time I don't seriously think I can "make it" as a pianist. I'm unable to throw away everything and play for 8+ hours/day on a regular basis, which is unfortunately what you need (in addition to huge talent) to win competitions these days. Not that I don't wish I could, and wonder how to make myself practice this much

.
So that's my personal issue.
On sacrifice in general: What (for example) Horowitz did wasn't a sacrifice. He loved the piano, and loved performing. He claimed never to have practiced more than 4 hours/day (a claim made by my own teacher as well), was happily married, enjoyed his hobbies, and probably helped his emotional problems by playing the piano. (Maybe it kept him sane. I sometimes think it keeps me sane). On top of that, he was one of the most respected pianists of the last century.
In contrast, if you sacrifice 8-14 hours/day practicing, don't have a social life, and fail to become a concert pianist, and also feel compelled to practice even when you don't enjoy what you are doing, and don't enjoy your lifestyle, that's a sacrifice - you have lost more than you gained.
I asked about sacrifice under the disguise of discussing a novel in the non-piano section:
https://www.pianostreet.com/smf/index.php/topic,10979.0.htmlI am also reading
Magister Ludi (The Glass Bead Game) (another Hesse novel) at the moment. Maybe I will have more to say when I have finished.
I haven't yet said everything I want to on this topic. Very personal, important, and alternately inspiring and disturbing.