Totally agree with mp, 100%, particularly her last para.
I didn't 'plan' my career as such but by studying hard and doing a medical type degree (physiology and pharmacology) I ended up always working in the medical field. I moved into medical/pharmaceutical market research (pretty specialised) and moved up the ladder there pretty quickly. When I had ds1 and wanted to leave, the MD was offering me anything adn everything to stay. In the end, I just didn't want to and they agreed to let me work freelance from home. I think the fact that I got on well with everyone, put in the extra hours blah blah meant they were happy to be as flexible as I wanted in order to keep me working for them in some capacity. The fact that I, by then, not only had a lot of market research experience and qualifications but also the medical background/knowledge means that I am paid a higher daily rate than most of the other freelancers that work on projects with me.
Sounds like a gloat but I'm really just trying to illustrate mp's point a bit.
Don't get me wrong, I'm certainly not loaded, but because of my daily rate, for the hours I actually work and the level of effort it takes me, I'm pretty well paid.
But really, although I've always studied and worked hard, it's mostly happened by luck rather than by design - I just followed a path I enjoyed and then 'fell into' jobs that suited me really. I couldn't have planned it - hence I agree with mp about specialising, working hard and getting on with everyone.