Gratitude
Developing a gratitude practice can help you feel happier. People who take the time to be grateful also tend to be healthier. This article on gratitude by Harvard talk about the basics of gratitude, gratitude practice, and reviews positive psychology research that has shown a correlation between gratitude, health, and happiness.
One way to practice gratitude is to recall 3 things you are grateful for before bed every night. You can say, think, or write these things down every night,