Finishing the last 5-10% of your game is the hardest part of making a game. It's the most daunting and the most horrific. For some reason despair kicks in. You start to play your game over and over and since you've been playing it non-stop since making it you start to doubt yourself and your game, you wonder if it's even fun anymore? you can't tell because you have tested it so many hundreds of time it's hard to know wether the first time someone plays it whether they will have fun. So you start to dwell on it. You also start to procrastinate due to the fear of releasing it. Thinking will it be good enough. I'm currently going through that myself right now with my new game that's almost done. It's particularly daunting because it's only my 2nd game in Unity since most of my previous work was done in Flash. It's also quite a big game.
On top of that your dealing with the least fun part of making a game, bug fixes, tidy ups, little changes, balancing the difficulty and getting it working on multiple devices. It makes you really start putting off finishing it. In fact I've known a lot of developers that don't even finish this stage of the development. They crack under the pressure to make it perfect and they just give up. It's always tempting, I'm not sure where this end stage despair and depression comes from inside us, but it's there. This is the part you need to use all your willpower and just push through it because it's all worth it the second it is done.
No matter what it is in life we find it easy to start new things because it's exciting and fun at first, but towards the end it's hard to finish them off due to the monotony of it all and the stressful things that pop up. This is a good time to write a small checklist, if you start to slow down, make it your goal to do one a day, once that list gets small enough you will find a surge of motivation to finish it off. Sometimes it's best to pull a few nights in a row non-stop even if you need to triple your caffeine dosage.
It's not uncommon for a developer to have to put more hours into the final 10% of their project then they did in the first 50% of the game.
Remember. Hang in there. Find that motivation on why your doing this, and push through it because it's all worth it in the end.