People can have remarkably keen insights into their own behavior. Then again, people can also be remarkably wrong about why they, and everyone else, do the things that they do. And some of those people turn out to be motivational speakers and authors.

No doubt their intentions are very admirable—many genuinely want to help others to reach a higher level of success. But too often, they simply end up reinforcing false notions (albeit intuitively appealing ones) about how works. Here are three of the most firmly entrenched motivational myths:

Just Write Down Your Goals, and Success is Guaranteed!

There is a story that motivational speakers/authors love to tell about the Yale Class of 1953. (Google it. It's everywhere.) Researchers, so the story goes, asked graduating Yale seniors if they had specific goals they wanted to achieve in the future that they had written down. Twenty years later, the researchers found that the mere 3 percent of students who had specific, written goals were wealthier than the other 97 percent combined. Isn't that amazing? It would be if it were true, which it isn't. (See the 1996 Fast Company article that debunked the story here.)

I wish it were that simple. To be fair, there is evidence that getting specific about what you want to achieve is really important. It's not a guaranteed road to fabulous wealth, but still important. In other words, specificity is necessary, but it's not nearly sufficient. Writing goals down is actually neither—it can't hurt, but there's also no hard evidence that writing per se does anything to help.

Just Try to Do Your Best!

Telling someone, or yourself, to just "do your best" is believed to be a great motivator. It isn't. Theoretically, it encourages without putting on too much pressure. In reality, and rather ironically, it is more-or-less permission to be mediocre.

Edwin Locke and Gary Latham, two renown organizational psychologists, have spent several decades studying the difference between "do your best" goals and their antithesis: specific and difficult goals. Evidence from more than 1,000 studies conducted by researchers across the globe shows that goals that not only spell out exactly what needs to be accomplished, but that also set the bar for achievement high, result in far superior performance than simply trying to "do your best." That's because more difficult goals cause you to, often unconsciously, increase your effort, focus and commitment to the goal, persist longer, and make better use of the most effective strategies.

Just Visualize Success!

Advocates of " " are particularly fond of this piece of advice. But visualizing success, particularly effortless success, is not just unhelpful—it's a great way to set yourself up for failure.

Few motivational gurus understand that there's an awfully big difference between believing you will succeed, and believing you will succeed easily. Realistic optimists believe they will succeed, but also believe they have to make success happen—through things like effort, careful planning, persistence, and choosing the right strategies. They don't away from thinking "negative" thoughts, like what obstacles will I face? and how will I deal with them?

Unrealistic optimists, on the other hand, believe that success will happen to them, if they do lots and lots of visualizing. Recent research shows that this actually (and once again, ironically) serves to drain the very energy we need to reach our goals. People who spend too much time fantasizing about the wonderful future that awaits them don't have enough gas left in the tank to actually get there.

You can cultivate a more realistically outlook by combining in your ability to succeed with an honest assessment of the challenges that await you. Don't visualize success—visualize the steps you will take in order to make success happen.

For more scientifically proven tips and strategies, check out my new book Succeed: How We Can Reach Our Goals or follow me on Twitter.