In Western culture we typically associate joy with external, conditional events. However, there is a form of joy that is unconditional and available in any circumstances. Scott Tusa describes this practice of innate or unconditional joyfulness as a radical act. You can find his article here: Joy is a Radical Act
Oren Jay Sofer describes the traditional Buddhist practice of appreciative joy, finding joy in the happiness of others, and connects the development of that practice to greater resilience in our lives. You can find that article here: The Resilience of Joy and Gratitude