If I had to choose a single discipline to have the most positive effect in every arena of my life, it would be Yoga. Now, the sneaky thing of course is that the term "yoga" covers a variety of linked disciplines, from the meditative to the physical to the social, so I've got most of what I need to be an awake, aware human being handled. If I had to choose one major division, it would be Hatha yoga, the science of posture"because while you can enter here and tie all the other aspects together, if you enter at the more esoteric aspects, it is quite possible to remain ignorant of, and neglectful toward, your body.
Seen it many times.
The number of different aspects that can all link here include health, fitness, ethics, psychology, stress management, social theory, epistemology, and philosophy. Good stuff!
But of course, it is possible to fall into traps with yoga, as with anything else. Injury, obsession, imbalance, rigidly dualistic thought, "dreaming that you are awake" and more area all possible negative side effects. Here are some thoughts based on my own fifty years of experience. (BTW--that experience was not all high quality. I first practiced yoga from watching "Yoga For Health" with Richard Hittleman on television, at the age of about eight. Other books and videos followed. I didn't start taking actual classes until my twenties, became more serious in my 30's, and finally attended a yoga teacher's training in my 40's.)
So. Ten thoughts on Hatha Yoga.
1) The quality of yoga is the quality of your attention, NOT the depth or amplitude of your postures, which are mere gymnastics.
2) You must learn the difference between intensity and pain. It is GOOD to take a yoga pose to the point of intensity, where you are challenged. But never let pain go above a "3" on a scale of 1-10.
3) Don't compare yourself to other people in the class. That mega-flexible teenager next to you might be a cheerleader thinking about her boyfriend as she ties herself in a knot. If your total focus and relaxation takes your head one inch closer to your knees"you're doing fine.