The Dirtiest Word Even Successful Entrepreneurs Still Use Every Day Saying 'no' takes practice. And confidence. And effort. But it's a skill worth learning.

As children, we were taught to listen to our parents, our teachers, our religious leaders, our baseball coaches. If you grew up in my family, however, you learned at a young age to respect adults. This meant not talking back, and saying "yes, sir" or "Yes, ma'am'"at all the appropriate times.

Related: I Started Saying 'No' to These 6 Things. My Life and My Business Got a Lot Better.

Society teaches us that to get ahead in life, we have to work hard, play nice with others and often complete tasks and projects we'd rather not do.

It's all a necessary part of the American Dream, right? You go to class, turn in your homework assignment, take the test, give the speech aand get the degree. Then, when you finally enter the workforce, you realize your "yes" career has only just begun.

Here's the problem though: Saying yes to every task or ask that you encounter doesn't always help you get ahead in your life or your career. On the contrary, it can actually hurt your ability to succeed.

Great leaders recognize the power of saying no.

Most of us are terrible at saying no (myself included). We weren't taught how to do it as children, and we're not encouraged to do it as working adults. For most of us, even saying the word is inherently uncomfortable. "Yes" is ingrained in our DNA, especially for those who live in the Midwest, like me.

But I'm here to tell you that it's OK to start saying no more often in your life and at your job, and here's why:

Successful businesspeople and great leaders aren't afraid to say the word. Take Warren Buffet, for example: One of the most famous business leaders,he's been quoted as saying, "The difference between successful people and really successful people is that really successful people say no to almost everything."

For Buffet, saying no is about eliminating distractions, about working on the things that matter most.

Related: How to Say 'No' at Work (Infographic)

His thoughts align well with what Steve Jobs once famously said about focus and saying no. "People think 'focus' means saying yes to the thing you've got to focus on," Jobs said. "But that's not what it means at all. It means saying no to the hundred other good ideas that there are. You have to pick carefully."

Even Jason Feifer, editor-in-chief of Entrepreneur, wrote about admitting we can't do everything, by focusing on what our time is worth.

These are just two examples, but there are countless others from entrepreneurs and other leaders, throughout history. These people understand the power and benefit of being able to confidently say no when it matters most.

When it's OK -- and when you should -- say no to people.

As good as it would probably feel to be able to say no to any project, task or person you encounter in your career, it's not a realistic way of approaching work. You're still likely to have to occasionally say yes to things you don't want to do. You have to pick your battles. So how do you recognize the times when you shouldn't back down -- when you feel in your gut that you need to say no? In my experience, those occasions occur when:

1. You're on a deadline.

If you know you need to focus on completing a task or project by a certain time, say no to projects that would distract you and ultimately impact your ability to succeed.

2. Your physical or mental health is at stake.

If saying yes might negatively impact or further damage your physical health or mental well-being, say no. Focus on keeping yourself healthy.

Jon Youshaei, founder of the cartoon site Every Vowel, discovered this the hard way. "In college, everyone told me to be an investment banker," Youshaei told me during a conversation on Facebook Messenger. "They talked about the prestige. The money. The opportunities. The money. And did I mention the money? So I did everything I could to land an internship in banking. When I finally did, I was miserable."

The following year, he applied for his dream company, Google, spending weeks designing a custom resume. And, turns out he got the gig. "My interviewer was so impressed that he asked to show my resume at future recruiting events," Youshaei said. "That moment taught me the importance of focus."

He learned that saying no to good opportunities enables you to chase great opportunities. So, "Keeping all your options open isn't always the best option."

3. You're being asked to do something unethical, illegal or contrary to your values.

If saying yes would mean committing a crime or doing something you morally disagree with, avoid putting yourself in a situation that will only complicate your life down the road.

Sol Orwell, co-founder of Examine.com, has a policy on his personal site about keeping things simple. "[W]e don't do JVs. Or affiliate deals. Or endorsements. Or 'like' your page. Or share your article. I don't even give testimonials," he wrote.

"If you do want to send me a book," he continued, "please note that upon receiving said book it will be promptly recycled ... To clarify: this is not because I'm an asshole ... I have simply adopted this inflexible policy to remain true to why I do this."

4. You're being asked to sacrifice work-life balance.

If what you're being asked to do means that you can no longer invest in personal relationships or work-life balance, say no. Remember: work isn't everything.

As Sonya Lee, CEO and startup consultant for Mowie Media, wrote, "After the launch of my second tech company, I was working so much that I did not realize how tired I was until I literally collapsed from exhaustion. My team recognized this and encouraged me to take some time off ... Saying 'Yes!' to myself was the minute I started feeling like success had finally arrived."

5. You're being assigned tasks that you know could be automated.

If what you're being asked to do isn't the best use of your time -- especially in relation to tasks that could be automated or streamlined with tools -- say no and suggest a better solution.

6. The task doesn't align with the bigger picture or goal.

If the task or ask doesn't bubble up to the bigger picture about which you've agreed on with others beforehand, say no. Avoid projects that take all your time but don't get you any closer to seeing the successful outcome you're looking for.

Goldie Chan, a top LinkedIn creator and the founder of Warm Robots, wrote that, "It's important to have one clear goal, so that way it's easy to say no ... earlier this year, I began to focus on writing more, which meant that I was saying no to unpaid speaking engagements so I could prioritize writing."

7. You know deep down you can't accomplish the task.

If you know you can't achieve what is being asked of you because of your abilities or the deadline, be honest and say no. It's much better to be up-front and honest than to disappoint, fall short or permanently damage trust.

Related: 6 Instances When Nicely Saying 'No' Benefits Your Business

Wrapping up

Saying no takes practice. It takes confidence. It isn't inherently easy, but it's a skill worth learning and putting into practice in order to get ahead in life and in your career.