I've been a healing channel for decades. Facilitating healing for another and teaching healing arts and bodywork are my passions.
Many folks consider me a powerful healing channel, a Reiki Master. I call myself a "work in progress". Now being in a state of joy, love and happiness is nice to have, but giving and sending unconditional love to your client is paramount to me. And the most important part of mastering the healing channel is the detachment from one's own inner storyteller (ego) and a detachment from the outcome. If the Ego of the healer is allowed to chatter, then it will shut down the healing channel. Also, in becoming powerful channels, the third leg of the stool, so to speak, is intention. A shaman's intention on helping members of his/her tribe is 'do or die'.
As a master, I believe it is important to do your own inner work and inner healing, so that you can become a clear channel for others. If you still have judgments, fears, or other emotional baggage, then when you open a channel for healing, the channel will be healing you first and your client gets what is leftover.
Also I know the Usui Reiki school in Japan does regular re-attunements of their students at all levels of mastery and daily meditations geared towards this inner work. Unless you are the reincarnation of Buddha we all have more inner work to do. With my own students, I also offer meditations and journey work to move into more subtle inner work. And I have my teachers, readings, and meditations to continually work on my own inner stuff.
Most of the real Masters I know are kind, humble, empathic, intuitive and have done a lot of inner work to get to where they are today. And all of them consider themselves "works in progress". Why, because they know the inner work we all need to do is rarely ever completed in a single physical lifetime.
So what do you think it takes to become a Master Healer?