The psychology of a disorganized person depends largely on why they are disorganized. There are those that just don't seem to have their priorities in line. There are those that bury themselves in clutter as sort of escape from everyday life. There are some people that may have disabilities such as ADD/ADHD that prevent them from being able to organize their lives. Each problem carries with it a different psychology.
For those that just don't seem to have their priorities in line, life can seem a bit overwhelming. They want to be able to stay organized, but they put a higher priority on other things. They may put a higher priority on going to work every day, and by the time they get home they are too exhausted to worry about what their home looks like. Unfortunately, the cluttered home can often sap them of the very energy they need to clean it and get it organized, creating a vicious circle that they cannot escape without help. They often wind up pushing away loved ones because they cannot keep up their homes.
There are some people who use the clutter as an escape. If their homes are cluttered and they are unable to have people over, they can escape life, and don't have to deal with it. These people often are suffering from depression or anxiety or both, causing them to want to withdraw from others. They push away loved ones who try to help them because they aren't ready to deal with their problems. A part of them may want to change, but part of them resists change, making them confused and causing even more anxiety. They will only be able to overcome their disorganization when they are ready, and not before.
Then there are those who are disorganized because of something like ADD/ADHD. In their own way, they are organized, but not to the naked eye. They have a pretty good idea of what they are doing, but things can get out of hand and overwhelming before they know it. This is a person that may be in the middle of one project, and go to put something away, forget what they were doing before and move on to a new project. They would have finished the original project when they noticed it again, but they do have a problem remaining focused on one area. The person with this problem doesn't want to be disorganized. It just kind of comes with the territory. It can be just as frustrating to them as it is to those around them, but it's the way life is and they learn to live with it. Medications may help, but sometimes they prefer not to be on medications and that's OK.
No matter what the reason is for disorganization, it is a personal thing. For some, it's not a very big problem until it gets completely out of hand. For others, they may want to change before it does get out of hand. Unless it is causing severe problems, it may be one of those thigns that you just need to let go of.