From Dr. Becker-Phelps Psychology Today Blog: Making Change.  http://www.psychologytoday.com/blog/making-change/200910/why-the-way-we-were-is-the-way-you-stay

One basic element to consider in understanding how people struggle with change is self-verification. They develop particular ways of defining themselves and then find ways to support those beliefs. Having a secure sense of who we are is so important that some people choose to cling to it-even when they’d be better off changing.

Leslie defines the Stages of Change in this blog post.  I’m living through many, frequent, large changes.  I do not feel like I’ve been volunteering for these changes.  But I am an agent in them.  There are many things I control.  There are decisions I make … go left, turn right, curl up in ball on the couch and watch TV.  Leslie makes a great point about people being so committed to self-definitions that even when they are negative, we prefer them over change.

… we are going along, accepting and believing our definitions of ourselves. Knowing who we are gives us a sense of safety and confidence in navigating through life; so we are deeply committed to our self-definitions. When faced with problems, we are likely to defend how we see ourselves-not wanting to give up that safety and confidence.

Even if someone has a painful self-definition, such as I am a failure; they at least know who they are. This way of defining themselves guides them in them daily lives (i.e. I won’t even try something new because I’ll just fail); it also prevents them from seeing conflicting facts (i.e. I have succeeded at some things in my life and might succeed at this). So, they are generally not motivated to even try to change because being different is not an option. And, when they do try to change, it’s usually a half-hearted attempt; their first lapse sends them back to the same old “I’m a failure” thoughts.