Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Smile and Humor Therapy

Chronic stress [ For more on 'stress' go here: http://www.braingle.com/mind/534.html ] can cause an imbalance in the neurochemicals that contribute to elevating our mood and reducing anxiety. Fortunately, research has shown that you can reduce the imbalance simply by smiling or laughing, regardless of your actually mood. When you smile or laugh, your brain gets fooled into thinking that it is happy, and releases the corresponding neurochemicals. Laughter has been shown to have the following benefits.

1. Lowering levels of the stress hormone, cortisol [ For more on 'cortisol' go here: http://www.braingle.com/mind/629.html ]
2. Reducing blood pressure
3. Boosting the immune system
4. Improving respiration and circulation
5. Reducing pain
6. Reducing depression and improving mood

If you are having a hard time getting motivated to do something and you need a pick me up, try smiling or laughing out loud. It may sound silly, but it can actually improve your mood and get you thinking more creatively. So, when life gives you a frown, turn it upside down!
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For more mind exercises: http://www.braingle.com/mind/