I work 9-5 for a large company (100,000+ employees). I clock on each day, they pay me a great daily rate and I enjoy the work that I do.
Work doesn't define who I am and I am definitely not unfulfilled. I take French classes, dabble in photography and build the occasional web app. Once a month I take a 3 day weekend and go somewhere I've never been before. So far this year I've been to Switzerland, Belgium, Iceland and I'm shortly off to Madrid. I also enjoy cooking and going to fine restaurants.
The only reason I can afford to do these things is because of the money I receive from my work as a cog. Sure, I could try and grow one of my web app ideas, work a bazillon hours for the small chance that it takes off and I become a millionaire.
But what would I do then? Most likely the exact same things that I am doing now.
I'm not advocating working in a job you hate and avoiding following your dreams. I'm saying that working as a cog allows me to afford my dream, so don't be so quick to bag it.