Procrastination: the devil responsible for all shortcomings

I wish I could understand the psychology behind procrastination. Why, for God sake why, we just put things off, even those that are so important to us.
Sometimes I just sit and finish a work in a day or two, a work I have been putting off for months. I knew I had to do it, but just didn't. And when it is done, you wonder why you just resisted.
I have two methods that when I am in the mode works well for tackling procrastination: 1) just sit and start doing it. 2) No expectation no disappointment. Without any thought for the next phase just start doing it.

Here are some good Internet resources:

• Five Steps to Stop Procrastinating and Achieve Your Goals Today
• How to Stop Procrastination with 5 Success Secrets
  
• How to Overcome Procrastination in 5 Easy Steps