In my first year of graduate school, I got the opportunity to give my very first psychology lecture. The professor who taught the course suggested that I videotape my performance, so I could see what I did well and what needed improvement. When I finally sat down to watch the video, it was more than a little horrifying. My "um"s and "uh"s outnumbered the actual words 2-to-1. Even worse, I saw that I touched my nose over and over again while speaking, as though I were constantly monitoring my own sobriety. Somewhere along the way I had unknowingly developed some very bad habits, and unless I wanted to be ruthlessly mocked for the rest of my teaching career, I was going to have to break them.
Habits are learned associations. If you repeat the same behavior in the same situation over and over again, your mind makes a connection and a habit is born. Light up a cigarette enough times in your favorite bar, and eventually just walking through the door will make you reach for your cigarette pack. "Situations" can be emotional states as well. Start using profane words to express your frustration, and pretty soon you'll be cursing like a sailor every time you lose your temper. My um-ing and nose-touching were nervous habits - responses to the stress I felt whenever I spoke to a large audience, that probably become habits somewhere in my adolescence (Why didn't anybody back then tell me?)
Once a habit is formed, all you need is the situation or the cue, and the behavior that goes with it follows automatically. In other words, you act without conscious intent (or even awareness - I certainly had no idea I had become a nose-toucher). Most people have at least one bad habit of some sort that they'd like to rid themselves of, whether it's smoking, nail-biting, over-sleeping, cursing, slouching, or eating too much when we're nervous, depressed, or bored.
But what is the best strategy to use to break a bad habit? Should you try to distract yourself, to take your mind off of the habit-triggering situation? Should you remove yourself from the situation entirely, or avoid it like the plague in the first place? These strategies actually work very well when it comes to resisting temptations (like a plate of doughnuts, or a flirtatious co-worker), but not for breaking bad habits.
Distraction isn't useful because the habit-behavior happens automatically - you don't even need to be focused on what you're doing. Avoiding the situation altogether is pretty much impossible for most bad habits - how exactly do I avoid public speaking if I'm a professor? How can we avoid ever being nervous, depressed, or bored?
So to really break a habit, what you need to do is focus on stopping the response before it starts (or, as psychologists tend to put it, you need to "inhibit" your bad behavior). A recent study by Jeffrey Quinn, Anthony Pascoe, Wendy Wood, and David Neal shows that the most effective strategy for breaking a bad habit is vigilant monitoring - focusing your attention on the unwanted behavior to make sure you don't engage in it. In other words, thinking to yourself "Don't do it!" and watching out for slipups.
In their study, participants kept a daily diary for a week or longer, to record their attempts at not engaging in a bad habit (e.g., overeating, sleeping during an early morning class, smoking, getting nervous before a test). With each attempt, they indicated which strategies they had used: vigilant monitoring (thinking "Don't do it!", watching carefully for mistakes, or monitoring their behavior) distracting myself, or removing myself from the situation.
The results showed that only vigilant monitoring was effective in stopping bad habits. (A second study conducted in the laboratory, in which the experimenters manipulated which strategy participants used, produced the same results). When people think to themselves "Don't do it!" they are actually able to take their brain off autopilot and break the situation-behavior connection. Over time, use of this strategy will destroy the connection completely, and the habit will be no more.
Incidentally, this is exactly how I stopped my nose-touching and excessive use of "um" and "uh" while lecturing. I consciously monitored what I did with my hands and kept them away from my face at all times. I wrote "NO UMS" at the top of each page of my lecture notes, to remind me not to fill my pauses with nonsense words. I would videotape myself every so often to check on my progress. Over time, (and it definitely took a while), I broke my nose-touching habit completely, and my ums and uhs are now no more frequent than everyone else's. I'm sure that I still give my students plenty to laugh about, but that's ok with me. I wouldn't want to ruin all their fun.
J. Quinn, A. Pascoe, W. Wood, & D. Neal (2010) Cant' control yourself? Monitor those bad habits. Personality and Social Psychology Bulletin, 36, 499-511.