Tara Brach writes in Radical Acceptance: Embracing Your Life With the Heart of a Buddha,

We are uncomfortable because everything in our life keeps changing—our moods, our bodies, our work, the people we love, the world we live in. We can’t hold on to anything—a beautiful sunset, a sweet taste, an intimate moment with a lover, our very existence as the body/mind we call self—because all things come and go. Lacking any permanent satisfaction, we continuously need another injection of fuel, stimulation, reassurance from loved ones, medicine, exercise and mediation. We are continually driven to become something more, to experience something else.