Now that you've thrown out your irrational thinking, a little motivation is key to change. But how do you make that leap? Psychologist and marathon runner Michael Gilewski has found that the brain can achieve a state of habitual behavior through small successes—turning a once extraordinary effort into mere routine.

"Even when someone climbs Mount Everest, it's usually not his first time climbing," he points out. Perhaps motivation may simply be the product of positive reinforcement and repeated success.

PT asked five expert motivators—including an active-duty drill sergeant and a rock-climbing instructor—how they rally everyone from first-time dieters to hard-core soldiers.

Deborah Low is a certified weight management and lifestyle consultant in Vancouver, British Columbia.

"We have an all-or-nothing attitude: If we don't do our full hour at the gym, we may as well sit around and eat junk food. If you feel guilty and punish yourself, you may eat 10 cookies instead of 2. If you criticize yourself, you'll never change.

"Motivation is something we get from other people; but inspiration swells within us. Thinking 'I'll lose weight and then I'll be happy' is not enough. If we respect and love ourselves, independent of our weight, it's easier to make healthy choices.

"We struggle because we're fixated on the end result. We force ourselves to go to the gym, restrict food, measure and weigh ourselves. You let that number on the scale determine how your day's going to go. I ask clients to remember what it was like to play as a kid. You ran around, climbed on things—your goal was not to lose weight, it was to have fun. Being active gave you a sense of freedom, excitement and amazement. You have to reconnect with that emotion."

Chris Broadway instructs an Outward Bound outdoor classroom on Hurricane Island, off the coast of Maine.

"I set the tone of team spirit in the beginning; I teach one person a skill, and his or her responsibility is to teach everyone else. We let the students make their own mistakes. We expect students to have problems, as the activities we construct are a challenge. Discouragement can occur, but we celebrate accomplishments. Students set their own level of achievement. Some have a focus on the end result, but not everyone is results-oriented. Some want to measure success by relationships they form, by the process itself.

"Another motivating factor is how their experience here connects to their lives. We create situations where there are actual risks and perceived risks, as in sailing. We let the group navigate ahead of a storm, deciding when to pull back and when to move forward. We show them how to apply these situations to their own businesses or personal lives—calculate the risk, know when to take it or when to step back.

"It's so much more powerful when another student steps up to deliver the message of leadership. As instructors, we're always building their tool kit so they have the means to do that. With a group of 12, it's difficult to hide in the background. Even if someone's in a slump, he or she absolutely needs to fill a role."

John Joline is a climbing instructor at Dartmouth College.