There's an old adage in the Twelve Step rooms that says, "Bring the body and the mind will follow." That is very true because of the relationship that the brain and the mind have, where the mind is the product of the brain's activity: Once the brain changes, the mind usually follows suit.
We see that happening, of course, in the addictive process itself. The brain has over 100 billion cells on average, and each of them has up to 10,000 connections to other neurons. That's a gazillion pathways for information! Each neuron has a unique function to perform for the activities of the brain, ranging from lifting an arm to solving mathematical equations. When poisons such as alcohol or other drugs are inserted into the brain, these chemicals change the way some of these nerves function, including how they communicate with one another. In the most extreme sense, a person gets "high" as a result of this intoxication, which is really a side effect of having poisons running through the natural chemistry of the brain. The brain changes this way when a person is inebriated and their mind certainly follows. There is a tendency for people to say or do things they would not ordinarily say or do if they were not incapacitated by the alcohol or other drugs.
So, too, is it when the brain is deprived of these poisons that it attempts to return to normal. In early abstinence, the brain signals the mind that it wants the alcohol or other drugs, and we call those withdrawal symptoms such as sweatiness, tremors, nausea, etc. As time passes, the brain starts to shift back to what it was like before the alcohol or other drug was placed in it. This re-adjustment period can last for months or, in some cases, years depending on the severity of the damage that was done. This is not necessarily a comfortable process, and people in sobriety will want to appreciate the degree of adjustment that the brain must make on its journey back to normalcy.
One salutary aspect of this re-adjustment is that as the brain changes back, so too, does the mind. Once again, fueled by the fact that it can function without poison running through it, the brain sends out signals of activity that get interpreted by us as our functions of a healthy mind. Willpower is gradually restored, and we can dream and have hope for not only recovery, but also for other things in our lives. We become clearer in our thinking and planning, and executing plans becomes easier to do. We have more psychological energy. Emotional health improves.
The brain and the mind work hand in hand to make us fully functioning human beings, and - while active addiction to chemicals erodes that functioning - healthful thinking can be restored with sobriety.