I once learned a lesson about the importance of mental control while practicing when I spent most of a class mulling over a problem, and I couldn't believe the difference by the end. People usually leave class with a contented demeanor, and I recognized that day that, though I had done every pose, I was less relaxed because I had ignored the mind and body connection. The yoga instructors each have different styles and varying levels of knowledge and ability. Thus classes are varied, sometimes more aerobic, other times more slow and relaxing. Poses challenge your balance, strength, flexibility, composure and focus.
Competition never factors in.
I quickly learned that while practicing in a group, you must listen to yourself and your body. More often, I've noticed, people observe others in the class out of admiration for their abilities. Of course, any physical activity is necessary to maintaining one's health and can make you feel better. I find yoga provides more far-reaching and unique benefits, and I notice the advantages outside of class. I feel more peaceful and can more easily clear my mind of worries.