Just a quick tip, today, from my own writing experience.
Today I was writing a story for Five Minute Fridays[1. Yeah, I love a challenge. So what?!]. I wrote my first sentence and then a second.
As soon as I tried to write a third sentence I realized I had already written my last line. I had the essence of the story in those first two sentences. I had simply arrived at the end too soon.
So I put my cursor in between the two sentences and filled in the rest of the story.
Having the last line — the destination — already in place made it so much easier to stay on track in the middle.
Why not try this as an exercise?
Write “Once upon a time there was a _________”
Then write “And in the end_________”
Then go back and fill in the middle.
If you like what you wrote, leave a comment so we can come and have a look.