I’ve never understood why so many business employees still think it’s fashionable to display a negative attitude about their work and never seem to find a job they enjoy. They don’t realize that they are their own worst career enemies, since promotions and new opportunities always are offered first to people who proclaim to be productive winners, rather than sound like losers.

Top companies today, including Google and Zappos, have found that a work culture that includes some fun, populated by happy and positive people, leads to more productivity and success for the business as well as the people. In my years of business experience as an employee, a startup investor, and an executive, I have seen a host of reasons for these results, including:

1. People work more productively on things they love to do.

When you are having fun and are fully engaged on your favorite project, the time just flies by, and more gets done. Happier workers have been shown in studies to increase their pace (productivity) without sacrificing quality. That in turn increases their self-confidence and motivation to do more.

2. Happy people maintain a positive “can-do” attitude.

Negative attitudes are often a self-fulfilling prophecy, meaning that if you don’t think you can do something, you will usually fail. With a positive attitude, every new challenge, and there are many in business, becomes an invigorating opportunity, rather than an annoying distraction.

Related: 5 Inexpensive Ways to Create a Company Culture Like Google's

3. Relaxation tends to improve creativity.

Constant stress, tension, and unhappiness causes people to withdraw and reject new customer ideas or solutions. They find it hard to think outside the box, be creative, or be open-minded to peers and executives. That’s why companies like Twitter offer free yoga classes and free meals to employees.

4. Supportive group collaborations produce better results.

In teams, people that enjoy and respect each other feed off other’s energy and brainstorm more innovative answers. An unhappy member becomes a “downer,” and brings everyone down, or at least slows them all down. Productive group decision-making requires confident team members.

5. Positive team members are not afraid to make mistakes.

They know the joy of learning from failed fun experiments far outweighs the risk of being seen as failures. In the unknowns of a new business, there are no right ways or wrong ways, just new ways that need to be tested to satisfy customer needs and stay ahead of competitors.

Related: 3 Ways to Simplify Your Company Culture and Build Trust

6. Leaders like to be surrounded by fun, productive people.

If what you enjoy in business is new challenges and more opportunity, you need to be seen by leaders as one of them. If you display a negative attitude and unhappiness, you are less likely to get the trust and attention of people in a position to make a difference for you.

7. Happy people are not afraid to ask for and give support.

Smart people surround themselves with people they respect and trust, and don’t try to solve every problem alone. They swallow their pride, ask for help when things get tough, and actively listen and respond to recommendations. They also get satisfaction from mentoring others.

8. Demonstrate your leadership, or be happy as a follower.

Accept and capitalize on your own strengths and weaknesses. Not everyone needs to be a leader. Everyone appreciates a productive worker who does the hard work, makes no excuses, and gets satisfaction from positive customer and executive feedback. Enjoy your strengths.

In this new age of the entrepreneur, if you can’t find a job you enjoy in an existing business, it may be time to start your own business. According to a classic study by the Wharton School of Business a while back, those running their own businesses ranked themselves happier than all other professions, regardless of how much money they made, or how many times they failed.

Related: What Company Culture Is Really About

If you are one of those people who still insist on seeing business and fun as incompatible, I urge you to take another look. Fun is all about satisfaction, doing new things, stretching your mind, and productive relationships with others. If you can’t find that in your own business, or one of the many exciting businesses out there today, then I say you haven’t looked hard enough. Enjoy.