Why is sticking to a New Year's resolution so difficult?

France's Rugby Union national team's hooker Dimitri Szarzewski (L) and lock Lionel Nallet warm up during an indoor training session, on March 8, 2010 in Marcoussis, outside Paris, as part of the preparation of the team's Six Nations match against Italy. The match will take place on March 14, 2010.

It's the last day of January. So, how's that New Year's resolution you made while when you were nursing your hangover going? Are you sticking to it?If you are like most of us, probably not so well.

It's the last day of January. So, how's that New Year's resolution you made while when you were nursing your hangover going? Are you sticking to it?

If you are like most of us, probably not so well. Whether your resolution was to get more exercise, to lose some weight, to read the complete works of Shakespeare, or even just to get more sleep, there's a pretty good chance you made an effort, but didn't follow through. If you actually even ever made an effort to begin with.

Changing behavior, replacing a bad habit with a good one and embracing a new attitude are all challenging for humans, and there are some really good reasons why that's the case.

So, on this last day of January, we decided to call up New York Times reporter Charles Duhigg. He's the author of the best-seller, "The Power of Habit," which looks at the science behind habitual behavior.