Writing Is HardIt is really really effing hard. It seems easy. You think of a story, put together an idea, and put it on paper. Get some pretty notebooks, a purple ink pen, and let your thoughts bleed onto the page. Most people haven't actually TRIED to write a novel. They don't realize all the work that it involves, all the pain and anguish felt. The many versions of the story you go through, rewrites, and edits.
When you start out with that initial burst of energy it feels like you could go on forever. The words flow like honey over the pages making it stick to your eyes until tears begin to stream out. What happens when that initial burst of energy runs out? That dark place in the middle of your story that isn't fully developed. Sure there is a vague idea of what is supposed to go there, but will it be exciting enough to make the final cut of the book? Is it necessary to the main story? This is a critical stage of the novel where a lot of the character development and relationships are defined. Yet the middle parts aren't as exciting to write as the beginning or ending of the story. The journey to the final battle can be tough to get through.
The Plot HoleWriting is a marathon, not a sprint. If you think the entire writing process is like that initial Roadrunner sprint then you are in for a rude awakening. That Coyote has a rocket strapped to his back and he has writer's block on his side. At some point we all change the way we think about a story and have to go back to add information that we feel should already be there. We could forget to include something that is vital to the part you are writing now. Perhaps while editing you delete a whole chapter because it was boring exposition, but it relays information vital to the story.
That, my friends, is the problem of the soul sucking plot hole zombie Smurf. Finding it can be as much of a pain as trying to plug the hole. It can cripple your story and make it so your beta readers write in red permanent marker "WTF" all over your manuscript. If you need to plug a hole then figuring out where to add the needed information is a pain and can feel forced if it doesn't fit the natural flow of the story.