There are so many things that can be your block and several techniques to help you get on with it.
AlexK as usual, hit the mark. There's some part of you that doesn't want to do it. The real reasons are not always easy for you to discover. I believe becoming aware of the issues and dealing with them is best.
Some people are more practically minded and just want a formula, so here a few.
Nike: Just do it.
Blinders: Don't look at the obstacles or end, just the next step.
Inetia: Do some of it NOW, and do at least 20 minutes before taking a break.
Manager: Do it. Dump it. Delegate it. Decide which is appropriate and get on with it.
Trainer: Be your own personal trainer. Step back and give yourself some direction.
Just a note, people who are too busy to get things done seldom describe themselves a procrastinators. However, procrastinators will often busy themselves with other things. These types of procrasinators usually have something to confront before they can get on to it.
...EOR Iam2 
