[Meta][MF][Not actually a story][The MF tag was a lie] Any tips on actually finishing a story?

I've almost-written about 5 stories for this sub, but each time I do, I end up putting way too much detail in them. My most recent attempt already contains 25,000 characters and isn't even half way done yet.

Once I've spent about 6 or 8 hours writing, I start to lose arousal about the topic of the story and give up on it for the day. It's then really hard to pick it back up again to finish off. I've not written a 'normal' (i.e. non-erotic) story in a while, but I'm guessing they are easier to pick back up because with erotic stories I have to be really aroused about the particular story before I get back to it…

So, I'm either asking "How do I make my stories shorter?"

(Younger me would be confused – I could never write stories that were long enough before, and now they're all far too long… I hope one day I can say the same thing happened with my penis… ahem…)

Or I'm asking "How do you find the motivation to take an old story back up if you're only half-way done with it?"