Over Qualified...?

What makes people look for a different job or think of leaving their current job is a mystery for me up until now.  I've been with 3 different companies excluding my On-the-Job Trainee but yet I am still lost of what is the cause of this.  All I know, I've done this with different reasons with the various different occasions that I did so.

I have this experience in one of my interview, I was told that I am over-qualified for the position that I applied for.  That was the first time.  I had mix emotion about it - would I take it as complement or take it as an insult?  Regardless, it was the first time that I got rejected and feel okay about it.  In the back of my head, I was thinking - "So what?"

Qualification is a funny thing.  When I was starting out in my career I was considered to be the last choice since I am not qualified for the position, five years after and couple of promotions I am now "over qualified!"  I always thought I had to work harder than the rest contemporaries (at least those I share my graduation year) so that I can finally match-up with the rest of those whom I share my high school batch year. 

I spent 8 years in 2 universities to finish my degree.  My high school best friends were supervisors and managers already while I was reviewing for my board exam.  I thought I had to make-up, no matter what. 

Because of this thinking, when I was starting in my career, I became a workaholic.  Sometime I work for 24 hours straight.  I got sick a couple of times.  Got promoted a couple of times as well.  Nobody truly understands the motivation I had.  I went up the corporate ladder so fast that looking back now, I think I over did it. But then again -  I do not regret it.

So if being motivated makes you over qualified, then, so be it.  A company that can't see the relationship of diamonds to coal doesn't deserve to have any jewel.  Maybe I'm just being bitter though.