Old habits are like that Bruce Willis movie: they die hard.

It's quite difficult to quit doing something once your mind and your body gets used to it, experts say, because humans are creatures of habit.

We develop habits as we go about our life every day. Some people believe that a behavior becomes a habit after 21 days, while some think that it takes 66 days.

Whichever the case, some of those habits are not always helpful or healthy.

It's also not easy to unlearn a habit, but it is possible.

Why People Smoke

Experts say people who smoke often do so to relieve their stress and ease the pressure they get from work, school, or life in general.

For others, the urge to smoke is so strong that falling back to the habit seems like the only way to go, or that it's an old habit that has transformed into a second skin.

"Smoking is my best friend," said Barry Blackwell, one of the people featured in a series of portraits taken by professional photographer Laura Noel. Noel said she had wanted to capture photographs that depict why people smoke even though they know it's going to kill them, and amid public "repulsion."

For stress smokers, situations such as changing jobs or moving house may seem like the worst opportunities to quit the habit. These may even prompt the person to further do it.

A new study in the United Kingdom, however, revealed that these stressful situations could be the best time to ditch bad habits.

Making The Most Out Of Stressful Situations

The team of researchers from University of Bath were testing a theory called "habit discontinuity." This theory suggests that changes in behavior are more effective when they occur at the same time as a major life change.

During this major life change, lifestyle choices could be significantly disrupted, even temporarily, because people become open to new suggestions and information to make changes in their lives.

For the study, researchers recruited 800 participants to see if people would change their recycling behavior and lessen their energy use throughout the duration of the research.

Half of the participants had moved house within the past six months, while the other half had not.

The study participants received a bag of sustainable products that included vegetable and flower seeds, eco-washing liquid, a shower timer to help them make energy-conscious changes, and a bus timetable.

Those who had moved out were most likely to be environmentally-friendly than the group who had been living in the same abode, researchers said.

This suggests that there is a definite "window of opportunity" after a major life change for a person to change their habits. The opportunity lasts for three months, the study said.

"Life transitions, such as moving house or changing jobs presents a real opportunity to influence the choices people make. Often, around the time of a major change, life can be up in the air and as such as know that people are generally more open to new ideas and information," said Professor Bas Verplanken, the lead author of the study.

So if you want to quit the habit of smoking, one effective way to do it is while you're facing a major life change.

"The key is to find these opportunities if we're to help people make positive shifts that improve the environment and can save them money for the long-term," added Verplanken.

The team's findings are issued in the Journal of Environmental Psychology.

Photo: Cyril Caton | Flickr