Plan to keep at it for at least three months.
"Behavioral research indicates that it takes 90 days to prepare for change, build a new behavior, become confident in the face of high-risk triggers and move past the likelihood of relapse. Brain research also suggests that it takes a few months of practicing a new behavior to create permanent change. More than 75 percent of people maintain a goal for a week, but then they gradually slip back into old behavior. However, research shows that almost all of the people who maintain a new behavior for three months make the change permanent; the probability of relapse after that period is modest."
Excerpt from Changeology by John C. Norcross, PhD. Copyright 2012 by John C. Norcross, PhD. Reprinted by permission of Simon & Schuster, Inc., NY.