The simplest revelation is sometimes the most powerful.
I was practicing yoga at home recently, getting ready to float from reverse warrior into half moon on my left side. And then I remembered - that particular movement almost always causes a minor twinge of pain along my body's right side. Ironically, the pain stems from yoga. About a decade ago, I somehow injured that spot, probably by doing a posture incorrectly or moving too quickly, and I have to be careful to not enflame it. Yoga can be a wonderful healing tool, but as with anything, it also can cause injury. I'm reminded of the Latin phrase: "Quod me nutrit me destruit," which means "That which nourishes me destroys me." Angelina Jolie famously tattooed it below her navel.
I stopped. I thought. "If I know that movement hurts, why don't I not do it?"
Revelation. It's OK if you're laughing at me. Sometimes it takes awhile for me to get it. If something hurts, stop doing it. Not only in yoga and other physical endeavors, but also in all of life. Spiritually, mentally, emotionally. It's probably easier said than done and might not apply in all cases, but nonharming seems a good place to start.
As you might have guessed, there's a Sanskrit word for this: ahimsa. It means nonharming or nonviolence and is one of the five yamas of yoga. Yamas are a yogi's code of ethics and morals on how to conduct themselves in the world. Yamas are the first of eight limbs of yoga. Those postures you do in yoga class are the third limb, which should give you an idea of the importance of ahimsa in yogic philosophy.
Perhaps the first thing that comes to mind when you think of ahimsa is refraining from violence. That's probably a given, but there's more to it than that. Ahimsa also can mean your words or thoughts. Are they violent toward others? Toward yourself?
Another of my lifelong ahimsa practices is refusing to speak unkindly about my body or point out its flaws to others, as in "I don't like this or that" or "I'm so fat" or "I'm so old." This has been a long learning curve, but isn't all of life a practice in one way or another? We mess up or get off track and return, over and over.