Best writer's advice ever: Kill Your Children
In other words, whatever your favorite part of your writing is? It will be deleted eventually, because the story doesn't need it. So mourn Rosa, and then get on with the rest of the idea. It clearly has your interest right now, so run with it!
Fallout 4. Finally figured out the perks system, and now regret almost all of my prior perks. I'm level 35, and will never have a gun that does more than about 70 DMG, simply because I didn't put enough perk points into Gun Nut. Sheesh.
And I went back and did a couple of the earliest Quests, which I had been ignoring as I explored the world.... and managed to unlock some key information and functionality (like Trade Routes) that I had NO IDEA EXISTED.
This has transformed the game for me. Not "done" yet, but already planning my NEXT playthrough!