One of my teachers once described yoga as practice for death. I'm not sure precisely what she meant, but it feels true to me. Indeed, the final and most important pose in every practice is savasana, or corpse pose, in which you lie supine on your mat, often with a blanket draped over you (like a shroud), and release all your muscles, allowing the (dead) weight of your body to sink into the floor. As in meditation, you focus your attention on your breath and resist the temptation to scratch, fidget, adjust your limbs. Slowly, mysteriously, you begin to detach from your physical self. Dispassionately, you observe itches and twinges almost as though they were happening to someone else. And as you lie there, relaxed, dispelling discomfort with your breath, and accepting any residue that remains, you begin to feel that this might be something like death—and, incredibly, you can handle it.
For the year or more during which I was undergoing intensive treatment for breast cancer, I was beset with relentless anxiety about dying—except during yoga. The deep, slow breathing alone helped calm me on a physiological level. And the twists and stretches and flexes seemed to wring out the nervous energy that otherwise coagulated in my gut as dread. Letting go of any "goal" for each posture and focusing instead on the process, the actual experience, allowed me to yield to the present. Being fully in the present freed me (temporarily) from my fears about the future—particularly my fear of death.
In addition, there was something about recapitulating the movements of thousands of generations of yogis before me that made me feel as if I were part of an ageless process, and ageless myself—like a rock or a drop of water or air, eternal. And strangely, it was comforting instead of terrifying.
Maybe that's just me. And even I, enthusiast that I am, can achieve that equanimity only for moments at a time. But those moments are delicious and leave me hungry for more.