According to the Shambhala principles you should feel [sadness and joy, simultaneously] with everything you do.
Whether you have a good time or a bad time, you should feel sad and delighted at once. That is how to be a real decent human being, and it is also connected with the Buddhist principle of longing, or devotion. Longing is the hunger for sacredness. When you begin to feel you’re too much in the secular world, you long for the sacred world. Therefore you feel sad, and you open yourself up that way. When you feel so sad and tender, that also brings ideas for how to uplift the rest of the world. Joining sadness and joy is the only mechanism that brings the vision of the Great Eastern Sun.