Youtube letters

I have had days where I hit up to 10-12,000 words but I find I often jumble the stories eventually. I seem to be very good, or at least I am excited by, writing beginnings to stories, but I get tired of characters after awhile, and want something new. So I can write a lot of words but I have to keep changing stories. I don't really understand how authors write 1,000 page books all w/ the same characters.
I  suppose I feel like I "lose" the sense of why I am writing when it goes on that long, because a lot of scenes that get described in those types of books aren't what I call "big deal" scenes. For example, in a book like Under the Dome by Stephen King, he goes on and on oftentimes about minute details I would nevre dream of writing , but that are interesting to read nevertheless. He just describes the people sitting there having breakfast, or walking down a road, I dunno. Whenever I try it myself though, I just immediately lose interest. I get excited when I write the big deal scenes alone. It's like I often can't write anything but climaxes LOL!
I think it honestly comes from years of film watching combined with writing songs as well. I have tons of stories on my hard drives, but a lot of them are horribly fragmented with no clear end, and so I feel like I can't really ...like...send them anywhere. I am in the William Burroughs school of writing however :. I dunno. I just like doing it for the atmosphere, I like to zoom in and then zoom out of random scenes, it's my only sure fire method. For example now I am envisioning a scene : a woman in a house who figures out that she's a magician of some sort...I dunno...anything.... I'll take a scene like that and, just because I'm excited, I'll get maybe 2-3,000 words with it, joyously, but then...BOOM...i just get sleepy... and I never return to it, and I call it a short story.
I feel like there's a discrimination against short stories. I'm sorry for writing all of thsi LOL
Cheers and ciao and gracias for the video