Pace yourself. Start slowly.
I liken getting on the financial straight and narrow to trying to lose weight. One day 1 if you go out an exercise until you almost pass-out and eat like a rabbit all day, you will probably quit.
If you are very disciplined person, by all means go hardcore. Start a spending-fast. But the mere mortals among us might want to ease their way into the frugal life.
Don't be the fat-guy at the gym on January 2nd who burns himself out by mid-month.