Sit, take a load off.

It is the prefrontal of your brain that has to reconcile the artiste of your right hemisphere with the logician of your left, the tough guy of your hypothalamus with the drama queen of your anterior cingulae cortex.

Stay with me, it gets better.

All that seems like more than enough but then come the dorm rats and party animals of your midbrain, the place where your most decadent appetites - drinking, gambling, eating, smoking, shopping, sloth, sex, come to get fed.

Told you.

The battle between your noble lobes and ignoble ones isn't even close. Eating, having sex and sleeping are vital for the survival of the species, so evolution arranged for them to be irresistbly pleasureable.

Explains a lot, doesn't it?

Acquisitiveness is important too, so shopping and gambling carry kicks of their own. As for smoking, drinking and taking drugs, they have no survival value but they don't need to, since they sidestep evolution and pick the chemical locks of the brain's pleausre centers directly.

Sidestep. That explains quite a bit.

This article from Time magazine, Getting to No, The science of building willpower goes on to explain much about willpower and how the brain works.
We are complicated creatures and there is So Much about us that has nothing to do with willpower and everything to do with survival.

The bad news is that there is no pill, to fix this. We need to create new habits that take the place of old ones instead of just trying to go, cold turkey. I have seen cold turkey in action work, just once. Almost 40 years ago, DH stopped smoking in a weekend. He just stopped. He is also the one who can eat two cookies and stop. Would love to study his brain, because for most of us, it is not that simple. Most of us, sidestep. If it is true that we can learn to build willpower, as I look around at our world, now would be a great time to start...