This week, I shared some lessons I’ve learned with Startup Summer School attendees. One of the biggest was how important a cofounder is. I started CCAW as a solo founder. Even though it worked out—CCAW was a success—it was painful. Our progress was slower than it could have been and I was stretched super thin. I’ve thought more about why a cofounder is so beneficial. One word sums it up: accountability.

I often hear “not having to report to anyone” and “being my own boss” as top reasons for being an entrepreneur. But the most successful entrepreneurs are accountable to someone: a board of directors, cofounders, investors. Accountability leads to success. No accountability can prevent or slow your success. Why is that?

Accountability means that you’re expected to deliver on commitments by taking action. Others are relying on you. If you don’t deliver, there are clear repercussions for yourself and others. Translation: you can’t do whatever you want, whenever you want.

When you’re accountable to no one, you don’t have to commit. No commitment means no clear repercussions. Translation: you think you can do whatever you want, whenever you want. Entrepreneurship is all about taking action to meet a goal. But when you’re not accountable to anyone, you tend to take action when you want to, not when you need to. Over time, no action or slow action hinders you. And you shortchange yourself and everyone who works for you but doesn’t have the power to hold you accountable.

If you’re starting a company, try not to go it alone. And whatever you’re doing, find a way to make yourself accountable to someone.