If I were in your shoes, I'd find something I'm passionate about and build a business around it, especially with your knowledge of business administration. At 29 you've reached your prime :). I wouldn't go back to school and get more student loan debt because I could learn whatever I want for free from Kahn academy, or from all the videos put on line by Stanford and MIT, and I wouldn't work for peanuts in somebody else's office, but might consider an offer with a lot of equity. (Sorry for my dumb opinions. I'm just hoping to keep this thread alive long enough for someone smarter than me to join in.)
I'm 37. I've felt that way in the past. I've felt that way recently. I've had successes and I've had failures. Most people don't wake up and say "I've made it", if you are looking for that, it rarely comes.
I agree here, except with less concentration on "build a business around it". Find something you are passionate about and build the hell out of it (software, pizza, wood product). Don't build it for other people build it for yourself and become the best at it. I've failed at businesses that I thought were completely earth-shattering ideas, I've succeeded at businesses where people wanted the product and it was painfully obvious because they were already buying the product elsewhere.
