Why do we procrastinate?

It's a human tendency to enjoy ourselves now, and put off responsibilities until later....sometimes until the last possible second. We all know that procrastinating things we have to do causes us unnecessary stress, and we've all thought to ourselves "Why in the world do I procrastinate this every time?" We always tell ourselves, "I'll do it right when I get it next time..." but do we really? Why in the world do we procrastinate, just prolonging the inevitable?
I have a tendency to procrastinate little things that I think won't be a big deal to do last minute, but they eventually add up.
The biggest reason that people seem to procrastinate is that they want to live each day to it's fullest. To many people that means not doing work, doing enjoyable activities and relaxing. I must say, I have often put off homework because I wanted to go to the gym, or "I had to go to work last night, I'm just going to relax tonight." It's something we all do.
Another reason that we put off responsibilities is that we just don't really want to accept that we have piles and piles of things to do that are going to take hours and hours. We don't want to face the fact that we are going to have to spend an afternoon doing things we have to, instead of things we would much rather do. Responsibility can be a hard thing to face.
Most of us do eventually face the facts and do what needs to be done, no matter how close it is to the "deadline", but there are those poor unfortunate souls that the teachers are very familiar with. They are the people that put things off and put things off WAY past the deadlines and due dates. Eventually they have to do them or face dire consequences. Unfortunately by that time they don't have just a little stack of tedious tasks, they have a mountain of time consuming responsibilities that it may take days or weeks to emerge from.
Why, knowing that they will have to do it eventually, do people put things off for so long? Maybe they just haven't grown up yet. It really is a sign of maturity to be able to budget your time and get things done in a timely manner. Hmm....knowing all this, maybe I should go finish my chemistry homework....just kidding. ;-)