Recently Mark Cuban was asked what he would do if he lost it all. What would he do first?

"I would get a job as a bartender at night and a sales job during the day," Cuban said on the podcast How I Built This," and I would start working.

"Could I become a multimillionaire again? I have no doubt."

Why does he feel that way? Success is almost impossible -- in any field -- without solid sales skills.

Here's why. To many people, the word selling implies manipulating, pressuring, cajoling--all the used-car-salesman stereotypes.

But if you think of selling as explaining the logic and benefits of a decision, then everyone--business owner or not -- needs sales skills: to convince others that an idea makes sense, to show bosses or investors how a project or business will generate a return, to help employees understand the benefits of a new process, etc.

In essence, sales skills are communication skills. Communication skills are critical in any business or career -- and you'll learn more about communication by working in sales than you will anywhere else.

Gaining sales skills will help you win financing, bring in investors, line up distribution deals, land customers; in the early stages of starting a company, everything involves sales.

Understanding the sales process, and how to build long-term customer relationships, is incredibly important regardless of the industry or career you choose. Spending time in a direct sales role is an investment that will pay dividends forever.

Here are a few of the benefits:

1. You'll learn to negotiate.

Every job involves negotiating: with customers, with vendors and suppliers, even with employees. Salespeople learn to listen, evaluate variables, identify key drivers, overcome objections, and find ways to reach agreement--without burning bridges.

You'll learn to close.

Asking for what you want is difficult for a lot of people. Closing a sale is part art, part science. Getting others to agree with you and follow your direction is also part art and part science. If you want to lead people, you must be able to close. Great salespeople know how to close. Great bosses do, too.

2. You'll learn persistence.

Salespeople hear the word "no" all the time. Over time you'll start to see no as a challenge, not a rejection. And you'll figure out what to do next.

3. You'll learn self-discipline.

When you work for a big company, you can sometimes sleepwalk your way through a day and still get paid. When you work on commission, your credo is, "If it is to be, it's up to me." Working in sales is a great way to permanently connect the mental dots between performance and reward.

4. You'll gain self-confidence.

Working in sales is the perfect cure for shyness. You'll learn to step forward with confidence, especially under duress or in a crisis.

Still not convinced? Think of it this way: The more intimidating or scary a position in sales sounds, the more you need to take one. You'll gain confidence and self-assurance, and the skills you gain will serve you well for the rest of your business -- and personal -- life.

So if you're a would-be entrepreneur, set aside your business plan and work in sales for a year or two. If you're a struggling entrepreneur, take a part-time sales job. Part of the reason you're struggling is probably because of poor sales skills.

"Knowing what my sales skills are and the products that I am able to sell," Cuban said, "I think I could find a job selling a product that had enough commissions or rewards for me."

And that would generate enough seed money to let him start his own business... and let him use his sales skills to make money for himself, not for an employer.

Successful business owners -- successful people in general -- spend the majority of their time "selling."

Learn how to sell.

It's the best investment you will ever make.