A recent New York Times article links willpower to our sense of time. (http://www.nytimes.com/2013/11/17/opinion/sunday/youre-so-self-controlling.html?_r=1&). While I do not always agree with the author’s analogies (subways and brownies?), she discusses interesting research connecting the ability to delay gratification with the amount of time one waits for the reward. If the reward comes later than expected, or is inconsistent, we are less likely to practice self control.
This can have enormous implications in the use of willpower in diet and exercise. If the reward is weight loss, and we have not lost weight in the expected time we are more likely to give up. It may be easier to resist that brownie if we internalize how much longer the scale will stall by eating it. Uncertainty seems to decrease willpower.
If this is true, then the most obvious way to forestall the time trap is to set realistic goals. If you try to lose 20 pounds in a month, chances are you will give up very quickly as you will not see the results (rewards) you are aiming at. For success, set a more realistic and specific goal (lose 5 pounds in 6 weeks, or exercise for 30 minutes after work Monday, Wednesday, and Friday). Try a calendar or countdown clock to monitor progress. If you can alleviate the uncertainty of when you will get the reward (achieve your goal) you will be more likely to stick to it and succeed.