The Happiness Project
I recently read "The Happiness Project" by Gretchen Rubin. Rubin spent a year making and attempting to keep resolutions to become happier. I loved the book. It is rare to find a self-help book that is well written and nuanced. She encourages the reader to create a unique happiness project, and acknowledges that the specifics of her project only work for Gretchen Rubin. That's refreshing.
She took on a particular aspect of her life in each month, and February was about her relationship with her spouse. Of course at the Bay Area Relationship Center, we found this to be the most interesting chapter. Almost all of her resolutions in February were based on the research of the Gottman Institute. At BARC, we are very familiar with The Gottman Institute and we use the Gottman Method. Some of the Gottman tools she focused on were building the friendship in her relationship, being positive in interactions at least 5 times more often than negative, making repairs with humor during conflict, regularly expressing fondness and admiration, and creating rituals for connection.
She came up with a tool of her own, when she decided to secretly practice a week of "Extreme Nice" with her husband.
Rubin names a few other books she read in her research for February, but it sounded to me like most of her ideas came from John Gottman's book "The Seven Principles for Making Marriage Work." That's a book I would recommend including in your own Happiness Project.