One of the biggest challenges I had was taking my concept for a world and game campaign into cohesive game sessions that told the story I wanted to build with those at my gaming table.
I would forget to include things that I really wanted to 6 months ago. I had a hard time keeping track of where I was going and in the end it would occasionally devolve into me just rolling random monsters, because the week got away from me.
Then I discovered telling a story like I was writing a play.
The play would be your main plot of the campaign. The players need to do ____ in order to ____.
Every major book, tv show and movie uses a type of this formula. The fellowship of the ring need to get the one ring to Mount Doom in order to destroy it and bring peace to Middle Earth (for a time).
An act in a play is a subplot that drives the characters along until they can come to the final conflict and solve (or fail at solving) it. Acts can be split up by character level or events in the story itself.
The scene is your game session and how you move your players scene by scene to fulfilling the events laid out for them in each act and ultimately the entire play.