"To err is human," and that's just as true of business owners as it is everyone else. Unfortunately, as an entrepreneur, there are often consequences to your mistakes--some of which carry more weight than others. There are even a few that can totally crush your business, especially if you let them go unchecked until they drive your business into a downward spiral.

Sounds pretty scary, right? I'm dead serious. Educate yourself now, and make it a point to steer clear of the 11 mistakes below that could cost you your business.

1. Lacking Professionalism

No one likes a stickler. Everyone needs to loosen the collar a little from time to time, and that's fine as long you remain professional. Don't be the person who's known for making crude jokes, especially in front of customers. Leave the partying and social gatherings for the weekend. Monday mornings can be rough anyway, but having to face it with a salesperson who lets his weekend spill over into the workweek makes it unbearable.

2. Letting Customers Become Numbers

Every customer who interacts with you is a unique individual, and the person needs to be treated as such. The moment clients simply become a file in your database or a cell in your spreadsheet is the moment your business starts to fall apart. Make it a point to let your customers know you appreciate them and that you value both their current and repeat business.

3. Ignoring Customer Complaints

Most business owners don't look forward to handling customer complaints. However, they can't just be ignored in hopes they will magically disappear. View customer complaints as a chance to really shine and show customers they matter. Also, they give you the chance to gain feedback about your business and figure out ways to improve your processes.

4. Treating Your Time as Silver

Your time must be treated as gold and nothing less. Poor prioritization and mediocre productivity can quickly send a profitable business into the red. When it comes to time management, nothing less than the best use of your time is acceptable. Review your schedule at least once per week to ensure you're leveraging time as the most valuable asset in your business. It really is the one resource that can never be replenished.

5. Having a Major Meltdown

Having emotions is normal and appropriate. Letting them loose in the office isn't. If you fly off the handle at every situation, you'll show both your employees and your customers that you aren't a stable person who can be depended on. And if you've ever had an unstable boss before, you know how devastating this can be to office morale.

There are always going to be frustrations involved in running a business, but you don't have to let them jeopardize the loyalty of your customers or your staff. Temporarily walk away from situations that frustrate you to the point of anger. If necessary, take the rest of the day off. It's better to lose a day of work than an entire business.

6. Not Choosing Staff Carefully

Unless you run one of the 23 million solopreneur businesses in the United States, you're going to have to deal with the challenges of having employees. You probably already know that not all employees are created equally, but have you thought about the fact that a single bad employee--say, one who embezzles from company funds or sells trade secrets--can devastate your business?

Take the time to hire the right candidates. Doing so will ensure your customers are well taken care of--even when they're shaking someone else's hand besides your own.

7. Using Last Year's Methods

Complacency is a close cousin to inefficiency. Technology and equipment are constantly being updated, and it's up to you to stay on top of them by attending conferences, reading articles in trade publications, and networking with others in your industry. If you choose not to take advantage of advances in your industry, you'll quickly fall behind your competitors who choose a more enlightened approach.

8. Operating Unethically

One of the most sure-fire ways to lose customers is to allow unethical practices in your business. In doing so, you're sending a message that money is more important to you than people or doing the right thing. Do not tolerate unethical practices from yourself or your employees under any circumstance--it will sink your company.

9. Commanding a Robot Army

Your employees are people too, and they need to be treated with the same dignity and respect that you extend to your customers. Squeezing every last minute of productivity out of them without rewarding (or, at least, recognizing) their efforts will leave you facing an unstable work force and high turnover costs. The better you take care of your employees, the more likely they'll be to work hard for you and become brand ambassadors.

10. Choosing Quantity Over Quality

Sacrificing quality might bring in more orders, but will it result in return customers? Customers are quick to notice a drop in quality, and will take their money elsewhere if this occurs. Invest in your customers--and, ultimately, your future business--by focusing on ways to increase the quality of your products or services. The dividends will be much higher than the money you were trying to save.

11. Keeping a Death Grip on All the Responsibilities

As your business grows, learn to delegate tasks to others. It's hard to do, as most entrepreneurs really believe they're the only ones who can handle each and every task, but holding the reins so tightly compromises your chance to grow. When you learn to delegate tasks to others, you free yourself up to handle more important work by teaching others to complete tasks they're able to do without you.

You owe it to yourself and your business to both identify and prevent the mistakes that could cost you customers and revenue. Take the time to care for your customers, your employees, and the most valuable asset you have in business--your time.

Which cringeworthy mistakes have you encountered in your business? Share your experiences--as well as how you handled them--in the comments below: