A childhood belief about imaginary friends

I had a friend named Herman. He was, looking back at him, a shapeshifter. He was a Casper-like ghost, or an invisible flea that rode on my shoulder, or a disembodied presence, or a voice in my head, or some combination of them stacked on each other, so they were all Herman at the same time. He was an adviser, and another point of view to consider. Sometimes he was just there, not doing or saying anything, just, I somehow knew, enjoying himself. One day, he didn't say anything, but instead was getting ready to go away. I got very mad, and told him to go ahead and go. He did, and did not look back. I was sad for a while, but I got over it.