Oh! I get this feeling so hard. I was explaining some of the bigger stories in my head to my family on night (for whatever reason) I was talking about how I struggle to figure out filler-plot for the stories. I've got the beginning and ends figured out, as well as the characters, but I have a hard time doing the in-the-middle bits.
My mom said something along the lines of "You just need to sit down and write it, if you aren't constantly feeling the passionate urge to write than writing isn't really for you. If you really wanted to get this story down than it wouldn't already be written."
I love my mom, and she's a really nice person, but sometimes her life advice doesn't really suite me. I think she was trying to be encouraging, but it came off as the opposite. imo, passion for something that interests you can be fostered, and can grow with time (I've experienced this with drawing actually, so I'm pretty sure it does work). It's okay to be casual about a hobby, we're not all Branderson, we can't all write 2 books a year. If you want to be like that, that's great! But I firmly believe that prolific-ness is a skill, not a natural trait or talent. It can be built up over time, you don't have to born with it, or whatever. Lots of really famous "masters' in writing history didn't write very many books, and they took a really long time to write them.
Anyway, I just found this thread, and I will probably be here often lol, despite only having two (extremely jank) short stories and a few unfinished scenes to my name.