In 2006, the World Cube Association eliminated the "No Inspection" event for the Rubik's Cube. (For those of you who don't know, the WCA is thee governing body for twisty puzzle competitions.)
Every competitor was now allotted 15 seconds to pick up the cube to study it prior to their solve attempt. This gave them time to plan and predict their moves ahead of time...before they started. Some speedcubers objected to this pre-solve inspection time. They even tracked their own unofficial "No Inspection" records online. Don't get me wrong. A well thought out plan can build confidence and make the execution stage go more smoothly.
But for writers, you can sometimes overthink your story. Too much time spent plotting out your story can stifle your flexibility and creativity crafting your piece. It can even lead to writer's block if you're planning more than you're writing.
Sure, there are benefits to planning out structure, plot, setting, and or characters. I've done this before and it's like using a grocery list. Check off the items as you march down the aisles so you can get home to cook dinner. Doing this can save time. It can mean less revisions later. In fact, in my earlier post, "Are You Afraid of Process," I talk about the benefits of process applied to writing. Instead, make it an adventure. Jump in and start to write. Do a cannonball into the pool. You will have much more freedom to explore your story if you simply jump in. And what better way than to start in the middle?
One trick you should try is called "in medias res," which is Latin for into the middle of things. The premise is to start with the action before really establishing the setting, plot, or characters. You just might find out that your pink bunny character fired the shotgun for a much better reason than you had originally planned.
In any case, don't overthink it. Give yourself permission to explore. Start writing and see where it takes you. You just might surprise yourself.