This is a wonderful topic
It is wonderful because it represents the greatest dilemma of my so far brief life: become a scientist or a person who manages and works with people, with human beings?
What I'm going to portray might sound a bit shallow and even silly to you grown-ups

but I would like to present my microcosmic version analogue to the situation exposed on this thread.
I am 19 and must choose what to study at university

It would be easy for a person who focused his studies on a narrow field to say directly what he really likes, yet I harvested great enthusiasm towards both of two totally opposing ways of life: that of a "scientist" and that of a "manager"(or any person who is involved with people, and requires great social skills, charisma, politics, business etc. you understand what I mean).
Until the age of 16 I used to be a total "nerd", "without a life" and had the highest grades not only in science subjects but all fifteen subjects in my school. The drawback I never felt was the fact that I didn't have a social life, nearly no friends, never kissed a girlfriend, etc.
I simply liked what I did, and as a previous poster said, the fact that there were no interruptions to this continued study, this continued effort and work probably helped me to go on.
There was no balance between social life and spiritual/study life: I focused only on the latter and - I'm not saying this to boast - I used to be a genius.
And I continued that lifestyle, and probably would still be continuing it with full confidence if I hadn't had a
taste of what "social life"/"real life" means.
Infact, there was a period of just a few weeks during which I tried to
expand - not change! - and used my enthusiastic effort to carry out some business model and public relations projects which heavily relied on
people.
It seriously took me only a good full immersion in business success books, personal growth and social skill DYI books to suddenly become a "nerd" of social skills. I know this sounds freaky and banal, but at that time I really thought that I was studying something and not entering what's commonly called "having a life".
To apply what I learned in such books, I did it with the same effort I would have studied to get an A+ in mathematics.
And, folks - believe me or not - it worked and it seemed as if I was becoming some charismatic god or something (that's how I
felt when I was 16, at my first contact with other humans

). With time I obviously learned also the value of modesty and humbleness, but that small simple change made me have what I would have never ever thought of having before: girlfriends, the most beautiful, a role as an actor at a national theater, several assignments at real public relations tasks, and friends. Friends as I had never had before. A real exciting social life!
And you might think that those events "completed" me as a human being?
No. Just as the married scientists on the first post of this thread, I probably became too satisfied with what I had achieved.
And sometimes satisfaction can stagnate a person's motivation to go on.
For a long time I actually thought that I had
combined two lifestyles into one, but I realized after lot of pain that I was suddenly loosing all my scientific "talents" (if talents truly exist, I fervently believe that I had them. Because now I don't understand anything).
I was becoming an average student and understood my new "self" only when I got my first bad mark in maths.
I realized that I was too lazy to stay in front of the computer or books to study all the time and work with chemical formulas. I realized that I was actually scared to stay alone. Whenever I tried not to go to parties or stay with my girlfriend, I couldn't resist logging onto internet forums or MSN messenger - behaviours I never had when I used to be a "nerd".
I was becoming "people-dependent"! I couldn't live without a social life.
I actually complained these symptoms to the writers of all those self-help books and they told "come on mate, that's normal! that's life! enjoy the balance you have!".
I won't tell other details because otherwise I'll monopolize this thread, which is not my intention.
What I'm trying to say is: according to my experience it's damn hard to excel at both science-work and "having a life". You can excell in either one of them or have a balance in which you're only averagely good.
There are surely exceptions in the world out there, and success is, as the first poster said, surely a subjective term... but "the nerd inside me"

, the peaceful perfectionist I once used to be is telling me that I won't be truly satisfied if I don't excel in one or the other field.
Once I lived happily without even having
one real friend (apart from my hamster... now I'm addicted to humans, if that's a politically correct term.
And when I'm addicted to humans, I can hardly think
constantly about lightwaves, thermodynamics and fluids... but I can very well manage other people, speak publicly about the conditions of the world, organize humanitarian aid to tsunami victims, conduct a business project, and every other thing that has to do with... humans.
Yet, I must admit that I deeply miss my brilliance in natural sciences...
and that's my current dilemma: go back to my nat sciences, or live in the "real life"? Study astrophysics or economics?
This was my contribution to this thread, and I don't want it to come through as a vanity boast - we're online people who don't care about image and approval - and we do everything possible to be objective and sincere, right?