The other part, where fiction is less true than reality, means that fiction is more contained than fact. When you write fact you're always wondering what part to put in and what part to leave out. It all happened, right? But when you write fiction, you serve the story by including within it only those things that matter to the outcome of the story and the understanding of all the characters. Your character doesn't have to actually tie his shoelaces. He can just slam out the door. He doesn't have to slam the green wooden door with the brass-dragon-head knob. Do you see what I mean?
There's the kind of Authority, in Story, that serves your story perfectly, allowing you to know 100% of why and how everything in the story happens. Opposing that, is the desperation of not knowing how much to put in to start with, and how much to just fly with. Most people don't do enough work period. But I am fairly certain, given your clue about loving the fan-fiction as opposed to your own creative fiction, that the opposite is your problem. You do too much work in your own creative fiction before you let yourself fly.
Listen to what MPax had to say about being 100% in Authority over her story:
"I've started the spit & polish on my second novel this weekend. So, I've been putting myself in my main character's shoes. Been writing up character goals, motivation & conflict charts. I don't do that until after the first draft as I plot best when writing. It works best with the characters telling me who they are instead of the other way around. Then I write up sheet to focus and do the spit & polish."
-MPax, private communication
In other words, MPax just doesn't try to know 100% of what she knows she's going to have to know, in order for the story to make perfect sense in the world she has let form itself along the way. She just does her "reality check" at the end. I've never done that myself, but I can imagine it being "a blast", as she described one of her novels to me. That's what writing should be. A "BLAST"!!! And even more fun because until it gets published, it's all yours.
Going back to fan-fiction, Stephen, and finding it helps you to love your writing again, just has to explain why your "original" fiction might turn to slog for you - as opposed to the love and fun and excitement you have writing fan-fics (which are stories written in worlds and with characters other writers have created, the original story not being fan-fic, but something that allows the original writer to tell one story in one part of his/her world, and to have 100% understanding of why and how everything happened in that story, while still leaving, beyond those boundaries, a richness and edginess that provoke other writers to want to see more and more and more stories in that world, and so to write them themselves.) Boundaries in fan-fiction, being more or less pre-determined, allow you to relax, settle into a world you already know really well, with some characters you know very well indeed, and either use just them or introduce some new ones, and then create a new story beyond the boundary of the original story. Because you're relaxed and haven't had to work yourself to death to know everything about everything in this world with people you haven't had to slog over to make real and believable, then you can catch something amazingly like lightning, and write yourself a story and have fun again.