The Writer’s Struggle: Getting Started

I’m having a hard time getting started with my coming-of-age, dark fantasy. I’m going to try to write it from a first person’s view. It might not stay first person, but I think writing it this way might help me somehow. The narrator will be telling the story over twenty years after it happened. Can anyone out there tell me how something like this affects the storytelling? What is the difference between telling the story less than a year later and telling it twenty years later?