Exercise is a national obsession. Gadgets like the FitBit tracker and places like Soul Cycle have become household names, and people are getting into peak physical condition like never before.

Entrepreneurs need to be able to say the same thing about their minds. Leading a business requires being in peak mental condition, and thankfully there are things you can do to achieve this. These are some mental exercises that will give you the intellectual equivalent of being an expert marathon runner.

Mantra your way to happiness

The lifestyle of an entrepreneur is a pretty hectic one, and I freely concede that it's hard to smile when something goes haywire. But if you let it make you unhappy, it's hard to shake and easy to detect. When the boss is visibly unhappy, he/she unintentionally takes the whole team down, and it scares away even the most enthusiastic clients.

If you need an example of unhappy employees driving away business, just think about your last visit to the DMV. Do you want to go back there any time soon?

I recommend trying to be happy no matter how crazy things get. It sounds like one of those things that are easier said than done, but it's attainable. My mantra, "everything that happens to me is the best possible thing that can happen to me," has helped me tackle whatever the day brings.

Harvard Research has proven that just like unhappiness, happiness is contagious. So find your mantra, and eventually your office will beam along with you.

Push it to the limit

Owning a business is an extreme workout in itself, but it's not the entire workout. To become and remain a successful entrepreneur, you have to work constantly against becoming stagnant.

If champion Olympic swimmer Michael Phelps had stayed in the shallow end of the pool, what do you think would have happened to him? The same thing that would have happened if Oprah Winfrey had stuck with "AM Chicago"--her career would be a far cry from the Oprah empire of today. The most successful people always push past boundaries and seek new horizons.

Once a month, I lock myself in my office and think of ways to challenge myself and push LexION Capital to accomplish new goals, and you should do something similar. These goals don't have to be lofty. Once a day, you could think about one small improvement you'll make tomorrow, and after seeing it realized, let it evolve from there.

Withering criticism is good for you

I've appeared countless times as a financial expert on television. The first time I did many years ago, I was ecstatic. I was a star! Then, a fashion expert friend of mine said that she "almost vomited" when she saw it, and all of that joy abandoned me. Instead of running away sobbing--which I really, really, really wanted to do--I opened myself up to criticism and asked her to clarify.

She said my choice of wardrobe for that particular TV appearance was more shabby than chic, and as a result I had done myself and my business a disservice.

When someone says something that we don't want to hear, a lot of us dig in our heels, and I would be lying if I said that wasn't my first reaction. But I took her advice, and the next time I appeared on the network, it took things to the next level. She was right.

This exercise is the hardest one to stomach, since you're asking someone to point out your flaws, but encourage criticism, and absorb it when it comes. Maintaining an office full of "yes men" may provide you with some ego boosts, but it will do nothing for your business but supply you with paid liars. Meanwhile, criticism will show you the areas you most need to improve upon.

If you like having liars on your payroll telling you how brilliant you are, by all means hire them. Just be prepared to see your business fail, and trust me -having someone tell you an unpleasant truth is much less painful than looking at the smoking crater that used to be your business and asking yourself, "Why didn't anybody tell me?"