When I first was attuned to Reiki almost 12 years ago, my teacher did not stress or even mention how important it is for Reiki practitioners to ground themselves. Neither did my second teacher, who taught me how to attune others to Reiki and teach them the in's and out's of Reiki.
For the first several years on my Reiki journey, I still was in the dark about just how important it is to ground when doing Reiki. Then people began to ask me on Reiki social networks if I was grounding and how was I doing it? I was like grounding, what? Why? Apparently they thought it was important but I was clueless. So I started investigating and learned about sending energetic cords down from the soles of your feet and your tail bone into the earth in the form of tree roots.
I am reading a book about the American Indian take on Crystal Healing by Luc Bourgault and here is what he has to say "Next imagine roots of light disappearing from your feet into the ground. This will enable all surplus energy to become rooted. This way, if your patient releases bad or harmful forces during the treatment and your body receives them, they will not remain there. They will pass through your body into the ground, thanks to the roots of light you have created. This way you do not retain anything that could harm you. It is not even necessary to be standing on firm ground to imagine these roots of light. They will be just as effective if you are on the twentieth floor of a building."
In the world of Reiki, we believe that we are protected from taking on anything from our clients while giving someone Reiki, but I have found that if I ground myself before a session, the session is more powerful and I feel better afterwards. So I am now teaching the importance of grounding to my students, either right before you start a Reiki session, or as soon as you sit down and start giving your client Reiki. Can't hurt!