This happened to me.
I have a major fantasy work I’ve been working on since I was fifteen (so eight years), but even as I was constructing it back then I knew that I needed to be a better writer when I wrote the novel and constructed the major themes. I was laying the groundwork for my future self (who was hopefully a better writer) to go back through and fix.
I stopped writing this project around seventeen years old, because I realized I needed more life experience. I had spent two entire summers constructing this book (no exaggeration, that’s literally all I did, no friends, no nothing, just writing), and I felt like I carried it as far as I could go.
I started writing it again when I was twenty-two, when I had experienced more of life than I ever intended to. After experiencing a ton of trauma, one bad event after the other, I was subject to a pointless, meaningless existence, and I was all alone.
After I barely managed to drag myself out of that hell, I realized this is it this is what was missing from my story, all those years ago.
I think what compelled me to finally return to it, what convinced me that I was ready to take on such a massive project, was the need and want to pour all of my raw emotion into something. But it was the main character who guided me towards that want–the perfect vessel for my visceral hate.
I looked back at all of my old drafts. I’d saved every single one since I was fifteen years old. There was a lot of cringey stuff, and I wasn’t exactly the best at organizing which made me want to tear my hair out sometimes.
But, I think, at the end of the day what kept me going was the idea that not only did the story deserve to be refined and finished, but I also deserved to be able to write, finish, and expel the demons inside me.
In other words: It inspired me. Once I started, I couldn’t stop.
I don’t know if this will help, but my advice is to look at your story and find that aspect that inspires you. Hang onto that and see how you can expand that throughout your story, if you can learn to enjoy the process, writing it will be a lot easier. Still difficult, but almost fun.