I'm sure you have heard these things before, especially now in an age when positive psychology is so popular: Choose to be happy. Visualize your success and you will be successful. If you believe it, you can achieve it. They're nice messages, and they're everywhere.

But scientific evidence suggests that they may not actually be helpful when it comes to achieving our goals and being successful.

Instead, more than 20 years of research by New York University's Gabriele Oettingen suggests that positive imagery can backfire on us. It can trick the mind into relaxing, making it harder for us to get our work done.

Often it's negative thinkers who turn out to be the best motivators when it comes to getting things done. Here are some reasons why:

Negative thinkers are tuned in to the challenges ahead. Thinking about future obstacles helps you begin planning strategies to overcome them. When you're telling yourself everything will work out, you aren't planning. Negative thinkers have a competitive advantage in the face of difficulties.

Negative thinkers are two steps ahead of everyone. They think of solutions before the problem even appears. You cannot stop the waves, but you can learn to surf.

Negative thinkers undermine complacency. When most people expect everything to go as planned, negative thinkers are making a list of all the things that can fail. They're rarely caught off guard, and they always have a plan B.

Negative thinkers aren't so much pessimists as hard-edged realists. They can see not only problems but also opportunities before they arise. They're skilled at turning failure into lessons. They know how to cut through the bull and wishful thinking to see what's actually happening in front of them.

So maybe the negative thinkers on your team have more value than you've been giving them credit for. Remember, every point of thinking has value.