What do you do when you get stuck with something easy?

I have been struggling with this ever since I picked up writing a few months back. Writing on it's own is certainly hard, but editing makes me want to bash my head against a wall and pray my adhd ramblings will come together magically on their own.

I stare blankly at my screen when it says something that really shouldn't be hard for me to work with, but I can't think of anything. For example: Character A is upset about being pestered by Character B over what happened yesterday. All I have to write is Character A trying to get him to leave, whereas Character B is continuously persistent. Then transition to the next scene. It should be so easy, but for some reason I just can't write. I've written 10k words of these two and now I'm tired over a silly little scene like this? It keeps happening and I don't know why ughhhh