What the hell am I doing with my life?

Am I the only one who is struggling with what they're doing with life? I thought I had it all under control; I had finally picked a career and knew what I wanted to do for the rest of my life. Then I hit 26 and all of a sudden I have no clue what I want to do anymore. Do I find a new job? Do I go back to school? Do I just stick it out and continue with my current job?