Have you ever screwed up using your imagination? In imagination, anything goes, right?
Actually, people make mistakes with their imagination all the time. They imagine how someone will react, or what will happen with some physical system, and get it wrong. If your imagination were never wrong, you'd be able to predict everything pretty well. But of course we can't.
People even make mistakes about what is imaginary and what is not. In psychology they call these misattribution errors.
For example, sometimes you think you remember something but it's actually something you imagined. Psychologists call this "false memory." Whenever you recall something that happened, you recreate it in your mind, fabricating details on the spot without even realizing it. As you tell a story again and again, you remember it differently, slightly, every time.
I remember clearly trying to ride my tricycle down the stairs. I fell all the way down, with the trike falling after me, narrowly missing me as it landed at the bottom.
This actually happened, but I remember it happening in the wrong house. It happened before I was five, in a different house. I remember it happening in the home I grew up in.
For the most part, the things that happened to you before you were five are not remembered. This is called infant amnesia. You might think you remember things, but most of them are reconstructions based on family stories. Mine is a false memory based on the story. (Please don't clog my comment section with things you swear you remember from when you were a baby.)
The other kind of error is has the wonderful name cryptomnesia. This is when you think you've imagined something, but it's actually a memory. My man Joe Kraemer is a TV and film composer, and he told me that when he's thinking of some new tune, and one comes to his mind, he has to be careful that it's not something he's just remembering. I wrote a bit about this before in reference to Lady Gaga and Madonnna:
Pictured: Stairs, from Wikimedia Commons