I just want to recommend to you a TED talk about happiness and success:
Shawn Achor: The happy secret to better work
It has a lot of useful tips and starting points on how to become happier and, as a consequence, work better, be more productive, etc.
Here is a quote I loved:
"If happiness is on the other side of success, you'll never get there."
Also, a few simple steps for creating a lasting positive change:
- 3 gratitudes
- random acts of kindness