You can look at effort in the context when you need to make a choice that involves internal conflict. Part of you wants to eat more, while the other part thinks you shouldn't. Internal conflict requires you to move "uphill" or resist the easy flow.
Classic goal-setting theory says that you first set a goal, then you make a plan to achieve it and finally you start taking action. Recently, I've begun to question the wisdom of this approach. Now, I'm inclined to believe that, for certain types of efforts, you're better of setting goals in the middle.
Uncertain goals should be set in the middle. This will enable you to set the correct challenge level to maximize effort.
Some research shows that for very complex tasks, goal-setting can hinder effectiveness. This is because complex tasks are cognitively demanding in the beginning and can be frustrating because you can't perform adequately. To add on more tasks can impair your performance.
Recently, I wrote a piece about how to commit to the things you start. In it, I argued that most people are spectacularly bad at committing to things which don't have a culturally or socially-enforced system of accountability. This is unfortunate, because being successful in life inevitably depends on either doing things that weren't mandatory ...
You're supposed to write an essay, but you procrastinate. The treadmill is collecting dust in your basement. You want to learn a language, start a business or change careers, but those ideas go nowhere. Inaction is something we've all experienced. Inaction, more than anything else, is the cause of our failures and our miseries.