Feeling unmotivated?

You've got to the part in your story where the honey-moon period has faded away, and the finish line is still far off (usually when you've hit the middle especially when the part your writing seems like one of the less exciting parts).
Now you feel unmotivated and this could just be your next unfinished project.
STOP.

That's my advice to you. Stop writing. Take a break. Travel to the Bahamas. Sip on a cocktail martini. Get a foot massage. Watch some dolphins do some flips and shit (The Lonely Island reference). Or if you don't have 20,000 dollars just lying around somewhere, then taking a break could include playing video games or taking your dog for a walk, whatever the hell you enjoy.
Basically take your mind off writing for a month or two. Hopefully after that, you'll feel refreshed and looking forward to writing the rest of your story.

Writing a story isn't a race. You shouldn't treat it like one. Take your time and enjoy your writing experience. If after writing 30,000 words you lose the feeling you had when you first started scribbling away...you know where you were really excited about all the characters and all the subplots and all the potential avenues the story could lead, take a break until you feel that love and excitement for your story once again.