[this is fun]

As everyone else has already said, it's a question of whether or not you really want something. I used to procrastinate with some things in my life. But that just keeps you in a limbo and starts to affect other aspect of your life, at least it was so in my case. I would put off doing/finishing something and I didn't have the guts to drop it and say okay I don't care about this.
Then I decided to sort of take stock of my life, of what's important or not. It was hard for me to be honest with myself and admit how I truly felt about things (as funny as it seems). Because I had invested so much time in something it felt unreasonable to drop it now. But I did it, I had had enough of it.

Like someone said, just do it now! Don't think about it too much. Maybe you could 'train' yourself with 'smaller' things first.

Or you could at first act as if you had to do it for someone else! That's what I noticed about myself, if I had to do something for someone else (help them in something ) I was always responsible, reliable, no matter whether or not I liked it I would even finish ahead of schedule!