3 good Things
Exercise Nº1
Focusing on the good improves wellbeing.
How it works
Every night, before bed, write down three good things that went well during your day.
It's important to write them down, but where you write them and on what is entirely up to you.
Why it works
This simple activity promotes a positive mindset by helping us become more aware of good things that continue to happen.
Further reading

The science stuff
(proof it works)
Research #1

Seligman, M. E., Steen, T. A., Park, N., & Peterson, C. (2005). Positive psychology progress: empirical validation of interventions. American Psychologist, 60(5), 410-421.
Research #2

Mongrain, M., & Anselmo-Matthews, T. (2012). Do positive psychology exercises work? A replication of Seligman et al. (2005). Journal of Clinical Psychology, 68(4), 382-389.