My observations:
1. Pay off debt as quickly as you can. When you're broke again, you'll be grateful you did.
2. Never put all of your eggs in one basket. When you only have one or two major sources of revenue (or clients), you're as dependent as an employee, but considerably less secure.
3. No matter how unnecessary it may seem, have a real, legally binding contract for any work you commit to do. I thought I did. I was wrong.
4. Budget for marketing. You can't depend on viral marketing alone.
5. Have health insurance. It's expensive and you can't afford it, and I know you're young and healthy, but when your appendix decides it's time to come out, you'll be on the hook for about $22,000.
6. If you're working from home, set boundaries. I won't work past 8pm, and I try to take one day a week off.
Ideally, you'll have some brilliant idea, already live frugally, have no debt, and a craft a bulletproof plan. Realistically, nothing can prepare you for the experience.