This is an excerpt from Journey Into Yin Yoga, A by Travis Eliot.
As a yoga practitioner, it is important to be able to discern the difference between good pain and bad pain. Part of the human experience is to feel natural discomfort within the body. Inevitably, in your yin yoga practice you will be in positions where you encounter difficult sensations, and this is quite normal. If you have been to a massage therapist, then you understand what good pain is. They frequently take their thumb or elbow and dig into knots of tension within your body. While this is happening, it doesn't feel all that good, and you might even notice a grimace on your face. But what happens after they finish working out the knot of tension? Chances are, you feel tremendous relief. Hopefully, the massage therapist also brought a certain level of sensitivity to the process. Even though they were digging into the muscle tissue, there should have been a quality of respect. When this happens, you will most likely return to that therapist for further treatment.
Your yin yoga practice, in a way, is like getting a massage. The main difference is that you are both the giver and the receiver of the massage. This means that if you are attuned to your body, then you should be able to find that perfect spot of discomfort that is beneficial without being too much.
How do you know whether it is bad pain? Feeling sharpness, numbness, or a burning sensation is your body's way of telling you that something is wrong. In this case, you have a few options. First, you can try backing out of the pose. Sometimes you have just gone too deep too fast, and the body isn't ready for that depth. Second, you might want to explore one of the modifications offered in the pose descriptions. Sometimes using a prop for support can help immediately. Any time the body loses anatomical integrity, the law of compensation kicks in. In the event of misalignment, other areas of the body are forced to compensate, and usually this strains these areas. Last, sometimes because of the way your body is built, some positions will never feel right. It doesn't matter how much stretching you do, the pose won't improve. In this case, find a variation that exposes the same muscle groups but is more suitable for your body.
Bone grinding into bone is never a good sign. Always look for the stretch within the deep fascia. It is common when coming out of a long yin pose to feel tenderness and sometimes a dull, achy sensation. Never rush yourself within the transitions. Allow your body the time that it needs to adjust to the deep stretch that it just experienced. Bring mindfulness into each and every movement.
Learn more about A Journey Into Yin Yoga.