There are already some good ideas suggested.
I think the problem may be in you expectations of work. You may be expecting if you get just the right job at just the right company, it'll change how you feel about work. The reality is you can't wait your whole life for the right change in job; the change must come from within.
Maybe you are feeling unfulfilled on a deep personal level and it's easier to blame it on work or age? What is it you feel like you're missing? What do you think you'd need to be happy?