“If I had more time, I would have written a shorter letter.”

Considering its ironic truth, it’s not surprising that the quote has been widely misattributed to Mark Twain. Nevertheless, a veritable who’s who of great thinkers, from Cicero and Martin Luther to Ben Franklin and Henry David Thoreau, have made strikingly similar statements.

When asked how long it takes to prepare his speeches, President Woodrow Wilson reportedly said that it takes two weeks for a 10-minute speech, one week for a half-hour speech, and “if I can talk as long as I want,” he said, “it requires no preparation at all. I am ready now.”

Brevity is more precious than verbosity. Simplicity is far more valuable than complexity. In so many important ways, less is more.

Now more than ever, having the discipline to focus only on what you do best is critical to success. It’s as true in your career and your business as it is in your communication. Sadly, more and more people – particularly aspiring entrepreneurs – are doing more and more. They’re spreading themselves too thin.

The thing is, if you can’t answer the question “What do you do for a living?” in less than five seconds, something’s wrong. Something’s very, very wrong.

A growing segment of the population is abandoning the corporate world and opting for the perceived freedom and flexibility of entrepreneurship — or so they think. The problem is they’re not focusing on creating innovative startups, but joining the growing ranks of the gig economy and doing a little of this and a little of that.

The data is startling. The U.S. labor force participation rate and new business creation are both at or near their lowest level in decades. At the same time, self-employed workers have ballooned to 16% of the workforce, up from 10% a decade ago, according to research from Princeton University reported in the Wall Street Journal.

Why is that a problem? In a word, productivity. A recent report by MBO Partners says that independent workers contribute just 7% of the nation’s GDP. In other words, self-employed workers are less than half as productive as their counterparts with full-time jobs. That’s a real problem.

This isn’t just about Uber drivers, Airbnb renters and Etsy marketers, mind you. The self-employment trend cuts across a broad swath of industries, geographies and demographics. Those workers often make ends meet by doing multiple gigs on a part-time basis. And therein lies the rub.

The more gigs you have, the less chance you have of developing differentiated, marketable skills and excelling in any single field. How many gigs is too many? More than one.

If social media profiles are any indication, folks certainly appear to have more irons in the fire than ever before. LinkedIn profiles are starting to resemble laundry lists like this one I recently came across: “Entrepreneur, Philanthropist, Career Transition Coach, Business Strategist, Transformational Catalyst, Author, Speaker.”

Look, there’s a very good reason why athletes focus only on one position in one sport. That’s what it takes to make it in a competitive world. Olympians may take the gold in multiple events, but always in the same category. Athletes may excel in many sports when they’re young, but the sooner they focus on one, the better.

Apple has long touted focus and discipline as key to its breakout success. Both Steve Jobs and Tim Cook have talked about the importance of doing only what the company does best and saying no to everything else. That’s why Apple can afford to control every aspect of its iconic products, from conceptual design to the customer experience.

Likewise, Google’s founders used to say, “It’s best to do one thing really, really well.” But when Eric Schmidt stepped down as CEO in 2011, the company unleashed a dizzying array of moonshots, from the infamous self-driving car and Google Glass to Wi-Fi balloons and the Calico anti-aging project. For four long years, the stock barely kept pace with the Nasdaq.

Since hiring Morgan Stanley CFO Ruth Porat, it’s like night and day. The search giant reorganized as Alphabet to increase visibility of its non-Google operations – projects it now calls “other bets.” That provided some much-needed fiscal discipline and accountability, and shares of Alphabet have responded, rising 88% in 29 months.

Every venture capitalist and startup founder will tell you the key to entrepreneurial success is focus and discipline. The same is true of your career. The sooner you figure out what to focus on doing and quit screwing around with everything else, the better.

A version of this originally appeared on Fortune.com.

Image credit Eric Robinson via Flickr