After a yoga practice- regardless of its duration- it's customary to rest in sivasana or "corpse pose." This supine posture is paramount to any practice, sealing in the effects of each asana, providing meaningful meditation time, and allowing the body to rest and rejuvenate. Following the pose and just before concluding class, students are typically asked to roll to their right sides, in the fetal position, before rising up to a seated posture.
But, why the right side?
Simple. Your heart is located on the left side of your chest; therefore, rolling to the right keeps your heart slightly more elevated for slightly longer. It's believed to be the most gradual, subtle transition out of your yoga practice. I often tell my students to think of this movement as "taking the yoga with them" before they go.
You don't abruptly end a yoga class and dive back into the chaos of your life, do you? Ideally, you bring the restfulness and reflection with you. In other words, the yoga never stops.