Here's a provocative statement: We change who we are literally hundreds of times during the course of an average month.
Of course our "core" selves don't change, but the face we show to the world does indeed change innumerable times, as do emotions associated with the face we're showing. For instance, during the course of an average day you might have breakfast with your spouse, attend a meeting with colleagues from work, have lunch with an old high school buddy, make a presentation to a client, go to the gym and work out with a trainer, have a drink with an out-of-town visitor, come home and shoot some hoops with your kid, call your grandmother, etc. In each of these settings you place yourself in an established narrative (e.g. I'm the high school clown, I'm the buttoned-up executive, I'm the solicitous granchild), and "take on" a somewhat different personna with accompanying emotions (the happy kid, the confident executive, the caring grandchild). In each different setting you would be exhibiting, to an outside observer, different aspects of your personality and interpersonal style. Personal identity is largely defined by the narratives we live out. Perhaps the best proof of this lies in the vast number of people who create alternative versions of themselves on the internet.
The key point I want to make today is that, at least to some degree we choose the way we want to present ourselves in each of these situations. The fact is that, before any encounter with most people or situations, we shift into a practiced version of ourselves that is such a well-worn path that the shift is almost unconscious, yet once aware of this phenomenon, it starts to become easier to track, and therefore alter.
The primary reason why it's so hard to change well-established narratives about ourselves, and hence patterns of behavior, is precisely because they're so well established. In my coaching work with many clients I find them feeling unable to alter their patterns of thinking, and hence their behavior. "I can't help it" is a very common refrain that I hear. Yet, the truth is that they can help it. It's just that it's either 1) very hard; 2) lacks sufficient incentive to make the change; 3) benefits in some way fromnot changing.
Reason #1 - yes, it's very hard to change established thought patterns. Most of these are formed unconsciously. There's a neurophysiological reason for this based on the fact that neurons in different areas of the brain that are stimulated simultaneously wind up creating patterned responses. A short article that dramatizes this principle clearly (as it applies to my former field, marketing) is: http://www.neurosciencemarketing.com/blog/articles/neurons-fire-together.htm
Reason#2 - If there's not an adequate reason to change behavior it won't happen. There needs to be an incentive powerful enough to create the motivation to (in neurological terms) "lay down new wiring". The incentive could be positive (e.g. a scaled bonus based on work performance or the group approval that underlies Weight Watcher's and, to some degree, AA's success) or negative (taking away a child's allowance for bad behavior; the disgust associated with clothes that are too tight because of weght gain). I sometimes suggest to clients who say "I can't help thinking / acting in a certain way" that if it cost them $1000 every time they indulged in the undesired thought or behavior they would pretty quickly change.
Reason #3 - Sometimes, behavior that on the surface seems to be counterproductive (e.g. constantly complaining) may have an emotional payoff (when I notice things that are wrong I'm smarter and more sensitive than the clods who accept this unacceptable situation). Or take the example of a person who's unjustly lost their job, but for months takes no steps towards finding new work; unconsciously they may be allowing the situation to worsen through inaction so that they can suffer consequences (running out of money) that truly prove how unjustly they were treated. Or they may have an unconscious association between feelings of failure and pleasure, stemming perhaps from when, after "failing." they were comforted as a child by their parents.
If there's a "you" that you'd like to change, let's talk about ways to make that happen. Those ways exist, and I implement them all the time with a wide variety of clients. It takes hard work, but they payoff can be spectacular.