I very often talk with my patients about practising gratitude, how it can help to set the positive set of mind. I found this easy to use app that I have been using for the past week and I already noticed some differences, it can be found : https://itunes.apple.com/us/app/three-good-things-a-happiness-journal/id1242079576?mt=8
Here is a paragraph explaining the mechanism.
People who are grateful tend to be happier, healthier and more fulfilled. Being grateful can help people cope with stress and can even have a beneficial effect on heart rate. This action is easy to do yet its benefits have been scientifically proven. In tests, people who tried it each night for just one week were happier and less depressed one month, three months and six months later.
From ancient scriptures to the latest science, gratitude is known to be good for us and those around us. Yet it isn't always our automatic response and we often take the good things in our lives for granted. So we have to consciously learn to get into the habit of being grateful.
Science is showing that gratitude is important for how good we feel psychologically and socially. It increases how much positive emotion we feel and decreases negative emotion. It raises our overall satisfaction with life and helps us have an overall positive outlook. It has also been shown to reduce health complaints and help us cope with difficulties. It even seems to reduce the importance we place on material goods. And contrary to what we may think, it also appears that it could increase our ability to achieve our goals.
Why does it work? We have a natural focus on what goes wrong in our daily lives often going over and over these things in our head. We are quick to notice even the smallest of problems, yet we rarely spend any time at all dwelling on the good things. Things that brought us a quick smile or felt good are all to often forgotten or perhaps not even noticed in the first place.
This action is simple but incredibly powerful. It's about taking the time to notice the good things in our lives and get the more from these. What's more, if parents remember to talk about the things they're grateful for, this can also help their children learn to think about the good things and hopefully get the benefit of a gratitude habit for the rest of their lives.
(borrowed from http://www.actionforhappiness.org/take-action/find-three-good-things-each-day)