Why do we do yoga?
If you look at what you find in the mainstream it's pretty much seen as exercise to make you feel better, get more flexible and to relieve some stress. All of these things are actually just side effects of the practice itself. There are many types of yoga, and group classes are simply asana or exercise. This falls under the category of hatha yoga which is the yoga of the body. You also have:
Karma yoga - the act of selfless service in order to give back to your community and to confront the ego at the same time by doing a task for others and expecting nothing in return. See the previous post.
Bhakti yoga - yoga of devotion, giving pure love from the heart to all things, maintaining a constant state of worship and separation from the ego.
Raja yoga - the scientific approach to yoga, systematically analysing the mind and applying techniques to bring it under your control. Hatha yoga also falls under this category by using the body to internalise your focus.
Jnana yoga - the intellectual approach to spiritual evolution. Through right inquiry and constant self-analysis the mind is used to examine it's own nature.
All of these practices can lead you to self awareness and waking up but only if done properly and consistently. That is the true practice and it requires a lot of discipline.
Regardless of what yoga class you find yourself in, the true goal, the true practice is to shut off your mind. It's not about what pose you can get into next or how good you look in those tights. It's more about observing yourself and confronting the ego so that slowly you can destroy it and realise that the sense of self is all an illusion anyways. That's an extremely hard task because the last thing the ego wants is to be confronted and questioned. In doing so you begin the process of separating yourself form it and that can be quite painful, emotionally speaking. Regardless of which way you intend to practice, your ego is your worst enemy and will always try to find new ways to hold you back. When you go to the quiet place that the focus of a yoga practice gives you.... look around, observe and question the very nature of who and what you are. When the ego is observed it is slowly destroyed.
I'm more of a jnana yogi myself these days though I kind of always have been. My quest started with wanting to know more about what was really going on around me and who I was in all of it. Finding hatha yoga gave me that moment of peace to truly learn to begin to focus my mind which in turn lead to a strong jnana yoga practice. But, my practice has been a combination of all of them over the 20 years that I have been doing yoga. There is more than one way to get to the top of the mountain I guess. The point is simply not to stop. Whatever way you choose to practice, whatever path you choose to take, just keep in mind that the heart of yoga is to separate from the ego in order to live your true nature. Don't lose sight of that.
Keep up the good fight.