What’s the biggest mistake you made in your first business venture?

Starting a business is a rollercoaster of excitement and mistakes. No matter how much research you do, some lessons can only be learned the hard way.

For those who have launched a business—big or small—what’s the biggest mistake you made in your first venture? Was it poor financial planning, trusting the wrong people, pricing your services too low, or something completely unexpected?

Looking back, what would you do differently? And what advice would you give to someone about to start their first business?