Lacking ambition?

I read an article earlier this year that said we lose our ambition at work when we hit 35.  I think that may be true for me, I certainly don't have the drive that I had when I was younger.  So, why have I applied for another post at work?  That's one of the questions I'm asking myself, but with an interview tomorrow it's a bit late.  It's been 5 years since I had any sort of interview and I'm not looking forward to the grilling on what I've achieved or the 5 minute presentation I have to give on how I'd take the role forward!  Mmm, better do some preparation then...