When we share in someone's joy, it is a heartwarming experience. It's part of human nature to feel happy when those around us are happy. "Rejoicing with" can be expressed in different ways, such as celebrating, exulting, or reveling in someone's joy. We can also use words like delighting, relishing, or savoring to describe how we feel when we share in another's happiness. Being able to empathize and share in someone's good fortune strengthens our relationships and brings us closer together. So, whether we're exulting or savoring someone's happiness, it's always a good feeling to join in the celebration of someone's success or achievement.