One of the simplest yet most effective exercises in positive psychology is a Gratitude Journal. Evidence has shown that developing gratitude for the things in our lives that we might otherwise take for granted, can have a big impact on our outlook and satisfaction with our lives. 
When we count our blessings we tend to be less depressed. Research was done on a university group. Students who were attending for counselling for depression or anxiety were divided into 3 groups. Group 1 did some gratitude journaling, Group 2 did some journaling about daily experience and Group 3 just attended counselling as normal. Those doing gratitude journaling showed greater improvements in mental health even 12 weeks after the experiment.
Gratitude shifts our attention away from negative emotions such as envy, resentment and social comparison.
Gratitude has lasting effects on the brain. Those who practise gratitude have greater neuronal activity in the prefrontal cortex which is good for mental health.
Gratitude is a powerful emotion. Merely by identifying and naming the incidents and the people we would like to thank we feel more positive on the inside. 
The practice of keeping a gratitude journal is quite simple. Get a notebook or journal that you can dedicate to this practice every day.
- Every night before bed, write down three things that you were grateful for that day.
- Alternatively, at several times during the day, pause and allow into your conscious awareness specific situations that you are really grateful for, these can be very tiny things.
- Think of particular details from the day or week, rather than something broad or non-specific (i.e., “the warm sunshine coming through the window this afternoon” rather than “the weather”).
If you have trouble thinking of things that you are grateful for, try thinking about what life would be like without certain aspects. This will help you to identify the things in your life that you are grateful for.