We all imagine having an audience for our writing.
Sometimes when I'm writing, it's an amorphous general audience of people who will one day read what I wrote. When I write in my journal, I write to my cat who has passed on. She is my audience. Sometimes I have a very specific larger audience in mind, like cat lovers when I wrote Mirabelle's Memoirs: A Feline Tale. Sometimes I'm not aware that I have an audience. But I keep writing.
I work as a writing coach with dissertation students, and these students often visualize their dissertation committee members reading their work. In this case, it's extremely important that they see that each committee member is gratified by what they are reading. Any audience needs to be pleased to be reading what you wrote. Visualizing having an enthused audience is like having a cheerleading team cheering you on.
A woman I worked with who was writing a book proposal visualized a very specific literary agent reading her proposal. She got excited as she saw the agent (in her mind) being fascinated by her project. A screenwriter saw his play being read by the actors who would be performing it. This enlivened him and allowed him to see opportunities for the characters that had formerly eluded him. Another person with whom I worked was writing the stories of several mentally ill women she had seen in ongoing psychotherapy. She spontaneously saw the women reading the stories and getting great pleasure from them. This empowered her to write more and to write more easily.
Often, the audience will spontaneously come to your mind. If that happens, notice if, grab onto it, embellish it. Make it rich and alive in your mind, your spirit, and body. Let it really nurture your writing. See, hear and feel your audience as if they are there. Right now. In the moment.
If you don't spontaneously visualize an audience, you can be your own audience. You can be a cheering squad of one whose voice is loud enough and whose presence is large enough so that you will keep writing. And, remember, if no audience comes to you, and you choose to not be your own audience, write anyway.