About five years ago, I wrote a blog post on willpower. It has been suggested in the comments of that post that willpower is not necessary. You can kinda go on autopilot and you're biology will somehow take care of it. Probably something along the lines of "listen to your body and it will take care of itself." Of course this is wrong.
The "listen to your body" brigade/proponents have overlooked a rather important but salient point which I will get to.
Lets look at a few scenarios (and see how they fare)
1. A guy wants to quit smoking. He throws away his cigarettes and adamant he's gonna quit. Everything appears fine for a while. Until the desire for a cigarette hits!
2. A person wants to lose weight. Selects a diet with which they feel comfy and sets off on their weight loss odyssey. Everything seems fine for a while until the munchies hit!
3. A junkie decides he's had enough. Wants to give up heroin/crack/meth. Decides to go cold-turkey. He's fine for a few hours, until the first withdrawal symptoms kick in.
In these three examples, a person is trying to break a habit. To establish a new habit. In essence, reprogramming themselves. The individuals have to overcome desire for external stimuli.
4. A guy wants to get fit and decides to take up running. Its cold, dark, wet, miserable outside. He puts on track suit and running shoes, then heads out the door. He's running in the cold, wet, rainy night. Huffing and puffing, his breathing is shallow. His legs hurt. He's cold. He feels awful. The desire to quit and head back home, to sit in the dry and the warm hits him.
5. Guy in a gym lifting weights. At the start of his exercise routine each workout, he sets a target for himself, of the weights and reps for the session. As he works each rep, he feels muscle burn. The build-up of lactic acid causes pain. Hurts him bad. The more reps he does the more lactic acid build up translates into more pain. The pain is a signal to stop. It hurts so bad, he feels he cannot do another lift. Thoughts run through his head. !STOP!
6. Guy get to bed late. Has an early appointment the next morning. Sets his alarm clock for a 6am call and drops into the depths of deep sleep. What seems like moments later, a shrill sound penetrates the darkness of his sleep. His eyes are burning. He's tired, too tired to climb out of bed. He reaches over to turn off the alarm. I need sleep. The desire for sleep is strong. What does he do.
In the last three examples, the individuals had to overcome conditions. Whether the conditions are cold and rain, muscle burn or lack of sleep.
In each situation, there is a strong desire to quit.
If we follow the "just listen to your body brigade",
The smoker will listen to his body and have a cigarette. The junkie will listen to his body and have a fix. The dieter will listen to his body and eat ice cream, cake and chocolate.
The runner will go home and sit in the warmth. The weight lifter will do no more reps. The sleeper will switch off the alarm clock and get forty winks, along with missing his job appointment.
In these above six examples, the only way to counter the desire in the situation at that moment is... willpower. The willpower to counter whatever negative feelings/desire you may have. It is only through willpower and determination that you overcome adverse conditions, feelings or desires.
But it takes effort. Real effort. Sometimes through gritted teeth.
These are a few situations I high-lighted. Its a non-starter to suggest that willpower is not necessary.