When I Grow Up....

So recently, I was speaking with an intelligent, successful friend about her current job (something in the financial sector). I asked her if she liked what she's currently doing better than her previously held position. Her response was something to the extent of: I like it enough; it's good/decent, but I don't know if this is what I'm really passionate about/what I really want to do with my career; I'm still not sure what I really want to do.

This reminded me of when I first started at my current company. I remember once during a meeting with the department VP, he asked me what I wanted to do 'when I grow up' (for lack of a better way of putting it). He went on to say 'it's all right if you don't know - I honestly don't really know what I want to do either'. I remember thinking 'well, you're 40, married with three kids, the primary breadwinner presumably, and you've been with this company 6 plus years in a VP position; I think this is it'.

So this leaves my question: does anyone know what he/she wants to do when he/she grows up? More importantly, is anyone doing it? (Sidenote: I realize there are a lot of people who do, indeed, know what they want to do an are doing it. A good amount of peole I know in the field of healthcare or education seem to be pretty satisfied with their career - or at least feel that it's what they want to be doing. I suppose this question is mostly geared toward the business sector.)

I seem to remember when I graduated college - I pretty much was looking for any tolerable entry-level job in any line of work. Whenever I was asked what I wanted to do in terms of my career, my answer was always some variation of 'oh, definitely this!', not because it was accurate but because I wanted (well, needed) a job. I know, for a lot of my friends, it was the same. I think a lot of people in my age bracket got an entry-level starting-salary job in some field, took the job and worked hard to get promoted in order to make a livable salary, then when it came time to look for a new position at another company, he or she looked for work in the same field because 1) it was what he/she was qualified to do and 2) to maintain the same salary or better (seeing that starting over in an entry-level position in a new field might require one to take a paycut (not to mention the difficulties of getting into a new field when one doesn't have many qualifications, on paper, for the position).

Anyhow - is this how a lot of people ended up in their jobs? Is it that they ended up in some field because it's the one that hired them/gave them a chance, then they ended up with that as their career. Is this parallel to Sex and the City's taxi theory? Someone decides she needs a job, and her career ends up being the one that hires her at said time; a man decides he's ready to get married and the woman who is there at the time ends up being his wife?

I guess this could be similar to the question asked earlier about Mr. Right - is it better to go with the 'wrong career' than no career? Are there a lot of people in their 'careers' who feel as though they don't know what they are actually supposed to be doing? Is it possible to change careers in adulthood, with, say, all the responsibilities of adulthood? Is it possible to do so somewhat easily? Your thoughts?