Early January is a time when many people set new goals for them selves with a wide variety of outcomes. The Transtheoretical Model (aka Stages of Change) helps explain why some people succeed and some people do not. If we set out to make a change and treat it as a process with a number of steps we can dramatically increase our chances for success. On the other hand, if we decide to make a change “cold turkey” or otherwise do not make preparations for the change, we set ourselves up to fall short of our goals.
Here is a good description of the Transtheoretical Model.