Who hasn’t ever thought about improving their life, being happier or securing a state of contentment as a bedrock of life rather than as a fleeting moment? There are many writers that have tried, with greater or lesser success, to respond to this dream of the human being. In this sense I have wanted to contribute my grain of sand, relying on my life experience and my reading, giving the question a more practical and interactive approach. If you really want to improve your life and be happy, “HAPPINESS IN THE 21st CENTURY; Guide for a Full Life” can help you since you will not only read it but also interact with it through the many exercises and reflective challenges that are offered to you throughout the work.