First, keep distractions at bay as best you can. Silence the TV, your phone, the kids, your roommate. Make sure those around you know not to disturb your for a certain amount of time.
Next, make sure you stay on task. It's so easy to walk to the coat closet to hang up a jacket, and end up cleaning out that closet, when you were really hoping to clear off the kitchen table. Stay in the area you've told yourself you're going to work on today.
We all tell ourselves excuses. I've done it, too! No more excuses!
No more "I'll just check my email first."
No more "I'll have more time tomorrow."
No more "I'll get more done if I take a quick nap or walk first."
No more "It's too hard."
No more "I'll start the laundry first."
No more "I have to help others first."
You decided to tackle this project. You are completely capable of doing it. No more excuses!