Editor's note: Failure can be a beautiful thing. With the right attitude, an entrepreneur can take the message from what went wrong and turn it into something that will be right in the future. Portfolio.com has partnered with the Young Entrepreneur Council to offer real-world stories of mistakes and the lessons they produce. Come back each Friday for another column in the series.

It seems like such a little thing after you’ve been in business for a while, but one bad client can make you question your abilities when you’re starting out with a business.

I’d only been in business full time for about six months when I faced off with a client. The contract had been going well—or so I thought—and was relatively simple. I was creating the copy for a new site. The client hadn’t given me much to work with, suggesting that I get the basic information off the current version of his site. I didn’t like using copy that clearly wasn’t working, but the first few pages that I turned in seemed to make the client very happy.

At the end of the project, when I turned over about half of the site’s copy to my client, he basically threw the entire project into reverse. I got nasty email after nasty email about how I’d only rewritten the information on the current version of the site, that I’d done an awful job on the project, and that he wasn’t going to pay for the work.

It sucked in ways that nothing had ever sucked for me before. I cried every time I tried to figure out what to do. I sent that client apologetic emails, trying to figure out what I could do to fix things. All I knew was that I’d made this guy mad and that I needed him to pay me for the time I’d spent on his project.

He finally sent me about half the fee we’d previously agreed on, swearing that I would never get anything else out of him. The work I’d done was already up on his site, and I left it alone.

Every time I thought about that project, I would just get more upset, and it took me a while to figure out why: He was angry with me, and I didn’t actually think I’d done anything wrong. When I was finally calm enough to deal with the situation, I looked over what I had written and the emails that we had exchanged. I’m pretty sure at this point that I fulfilled all the terms of our agreement and that I got taken advantage of. I failed to make sure that I protected my own interests and that of my business.

I revised the way that I dealt with clients as a result of this one upset. I made certain that not only did I have a contract on file for each of my clients, but I also made sure that I had exactly what every client I worked with wanted in writing. A phone call wasn’t good enough. I added a revisions clause to my contract. I even tweaked the process I used for handing over final projects to clients.

But, more importantly, I changed my mind-set. I made myself a list of why I’m the expert—why people pay my company to work on projects, and why they can’t just ride roughshod over me. I came to the conclusion that what a client says about my work may seem true from his point of view, but I stand by my work (and the prices I charge for it). The same holds true as I’ve expanded: I go out of my way to do great work and choose team members who do the same. I’m not about to let someone make me, or anyone I work with, feel that way again.

If someone wants to go back on our contract after the fact, and it’s happened again in the several years since I started my business, I’m not about to let them. I’ll go after what I deserve, without being scared that one client could ruin me.

The author is a member of the Young Entrepreneur Council. The YEC is an invite-only nonprofit organization comprised of the country’s most promising young entrepreneurs. The YEC promotes entrepreneurship as a solution to youth unemployment and underemployment and provides its members with access to tools, mentorship, and resources that support each stage of a business’s development and growth.