If you are reading this, you probably resolved to change your behavior or improve your performance this year. Statistics are not in your favor. The entire health club industry relies on people failing to follow through on their resolutions (and yet taking a long, long time to admit failure).
Making a change is not so much a matter of discipline as it is a matter of habit. And any habit, by definition, wants to stick around. The tried and true method for changing a habit is to take baby steps, rather than relying on willpower. At Acclivus we refer to that process as successive approximation, getting a little closer each day to the desired behavior.
But if changing a habit is all about self denial (even a little at a time) it can become tiresome and we can get bored with the slow progress. So rather than denying yourself at all, try embracing a new behavior that is inconsistent with the current behavior. In my case, when I was finally able to quit smoking after years of failure, it was because I took up running and fell in love with it. By focusing on getting better and better at that activity, I was less and less tempted to suck toxins into my lungs.
So make sure your goal is clear and specific, take it a day at a time, and focus on the positive behavior you are gaining, not the undesirable behavior you are losing.