This from Tim O'Reilly (Lovely piece about how technologies don't just replace one another. Search for 3rd occurrence of "Displacive Fallacy"http://bit.ly/cJSAlb ) is a useful parallel about building your career. You bring an integrated set of skills and experience to your work with each passing year - and you may not be aware of how often you use skills from the "old you" into your present proefessional life.
Take a moment to read what he points out (if nothing else - and the rest is fascinating) and think about the additive nature of your career. You may not have done this since your last interview (the key place and time at which we often are asked about and then verbalize this). It will give you a new perspective.