Always do the Opening and Closing of your Reiki sessions. Some people call the opening of Reiki a Reiki Prayer.
What is it in practice? It is a request, a decree of affirmation to the Universe, literally saying what you will do.
Example: “I ask for help from all the beings of light in the Universe for this self application or application on X person.
There are many examples on the web such as “The Great Invocation” by Alice Bailey.
It is important that you FEEL in your Heart and use these examples to create YOUR own opening / prayer, putting your own energy and intention into the words to open your paths and connect directly with the Universe, not with creations / texts / patterns developed by other people, that while they may be great, were great for them.
Create your own path.
My personal suggestion for this opening is:
Invoke the Reiki egregora, masters, guides and spiritual beings that accompany you using the words you feel in your heart at that moment.
For the closing, when you finish your session of self-application or application in another person, verbally or mentally decree to the Universe your desire to close that session, releasing all the beings of light that accompanied you in this process and releasing the person and/or you to the world, expressing your gratitude.