What works for me: When ur planning ur story out, make sure u know how u want it to end (doesnt hav to be exact, a rough idea is good enough) this helps when ur writing the middle section of the story because u know what u r striving towards. Also helps with planning the story out and make sure ur story is heading somewhere rather than going around in circles.

But yeah it takes alot of focus to finish stories!

if you're writing a lengthy story, i suggest creating a plot that is different from other stories. i find that if you write a story minus the cliche plot, you'll be more inclined to write it and finish it. a story that's different from others is also more interesting for readers as they don't know what's going to happen in the plot. also, try to write something realistic. that way, it's easier for you to come up with filler chapters and plot ideas, rather than something extravagant that can't possibly happen in real life. another thing that helps if you find it hard to complete stories is to write one shots for a while. start with something simple and short that's easy to finish. sometimes watching movies or shows and/or listening to music or reading lyrics helps.
good luck with it though. i hope you get into the swing of things soon. c:

I write a ton of oneshots. the time taken to complete them is good, and you don't have as much to worry about. i'd say practice with those and them move on to longer stuff.

I usually write oneshots because those are stories I can start and finish in a reasonable amount of time, lol.
Those long stories that I do have are either inspired and motivated by characters (Psycho) because they're so complex that I simply cannot leave them behind, the live and breathe within me. Other long stories are motivated because of feelings (Maybe if I skip dinner) because they portray a strong feeling I feel often than not, they take quite a certain mood to write but they're quite easy to stay motivated to write.
So I guess - either feeling or character keeps me motivated. If I don't connect to either the feeling of the story or the characters I just ... lose motivation. ^_^ I'd say I have ups and downs though, sometimes one story is easy to connect to than another or maybe none of them are - so I write a oneshot.

You know that is a hard one
i start so many stories and forget them
the ones i tend to finish are the ones that were inspired by some STRONG kind of love or emotion. when the inspiration is really good, then i wont quit
or if i start writing and it gets off to a really good start, i tend to want to finish more than if it has a mediocre first chapter