What regrets do you have? I really regret not starting to aggressively pay off debt sooner. I took the financial freedom course at my church in Oct 2010. If we had gotten serious about it then, we'd be buying a house right now. I keep kicking myself for all of the times I just paid the minimum payments.
I also wish I hadn't held down 3 jobs in my last semester of college. My GPA suffered, and has kept me out of grad school (it's 0.07 too low).