In 2013, my article "13 Things Mentally Strong People Don't Do" went viral. It attracted more than 20 million views on and and Business Insider alone. My list was also featured on other websites, like Success, Psychology Today, and The Huffington Post, making it impossible to know exactly how many people read those 600 words.

As a psychotherapist and college psychology instructor, I'd spent over a decade teaching people about mental strength. It's also a topic I feel passionate about on a personal level (watch my TEDx talk to hear what inspired me to write the article).

Creating a mega-viral article was a dream come true--and being able to turn it into a best-selling book was definitely the highlight. It's led to a lot of other opportunities too--the Mental Strength e-course, speaking engagements, and a second book deal with a major publisher.

Since my article went viral, many other writers have created similar headlines. And while some of their articles offer valuable and accurate insight into mental strength and mental toughness, others miss the mark.

Decades of research have gone into studying the way people can grow stronger by changing the way they think, feel, and behave. So I wanted to take the opportunity to clear up some of the biggest misconceptions some writers are spreading about mental strength.

Here are five truths about mental strength:

1. Mentally strong people are OK saying they can't do something.

Mental strength doesn't come with super powers. There are plenty of things mentally strong people can't do--and they're not afraid to admit it. But sadly, I see a lot of articles that claim "Mentally strong people never say, 'I can't.'"

In reality, mentally strong people are happy to acknowledge their weaknesses. When it makes sense to work on them, they do. When it's something they aren't particularly motivated to change, they don't worry about it.

2. Developing mental strength doesn't mean you can't give up.

Lots of articles claim mentally strong people never give up. But just like everyone else, mentally strong people's goals change.

When the cost of working toward something starts to outweigh the benefit, they give up and move on. They're strong enough to do that.

They don't waste time working to solve a problem that doesn't have a solution. And they aren't so prideful that they have to keep going, no matter the cost. That's because they're mentally strong--not just acting tough.

3. There aren't any specific diets that will help you build mental strength.

There are lots of cringeworthy recommendations about what you should consume to build mental strength. But mentally strong people are just as diverse in their diets as any other group.

Some drink coffee. Some are vegetarians. Some like cereal for breakfast. So don't believe any articles that say you have to consume certain foods if you want to build mental strength.

While there is a clear connection between maintaining a healthy body and a healthy mind, there's more than one way to stay healthy. What mentally strong people eat for breakfast is far less important than their daily health habits. Just like there are a lot of different diets that help people grow physical muscle, there are a lot of different ways to build mental muscle.

4. Becoming mentally strong doesn't mean you're always positive. 

While mentally strong people often choose to look for the silver lining, they're not unrealistically positive. In fact, being overconfident or unrealistically positive can leave you unprepared for the realities you're about to face.

Yet I see many articles that insist mentally strong people are "always positive." It simply isn't true.

Building mental strength is about learning how to regulate your thoughts so they're not overly negative or overly positive. Mentally strong people are clear-headed about the realities of life, even when those realities are hard to face.

5. Building mental strength won't necessarily make you a high achiever.

There are some mentally strong people who have achieved incredible things. But plenty of others fall elsewhere on the achievement scale. And they're OK with that. So be wary of any article that claims you have to be a billionaire or an elite athlete to be strong.

Mental strength is about living according to your values. For some mentally strong individuals, that means valuing time with family over earning money. And it means doing their best at whatever they do--whether it's flipping burgers or being a stay-at-home parent.