Is the main battle of the enemy for the mind? Pastor stressed in the last sermon, the main battle between us and the enemy (Satan), is for the mind.

If it is, what hope is there for people with severe mental illness like schizophrenia, bi-polar, etc.

It would appear that the battle is completely lost in these cases vs. other cases where we can use our free will to turn against the enemy.

So how does this battle for the mind work and are some born into a losing hand to the enemy, as described above?

EDIT
This is a different question than the posted possible duplicate and here's why:

That question focus on "will they still be saved?"

While that is important, this question focus on hope while alive here on earth, not the entrance into the next life. 

If such a person has that type of illness, it is as if they are stuck to live in darkness. It would seem that the enemy wins over that person. 

In addition, that person can bring even more darkness to family members - and in extreme cases to many others (i.e. - random school shootings and guns in America).

Where is the hope for these people, while here on earth, to live in the light of the Lord?
This answer focuses on the first question, of whether or not the enemy's focus is on the mind.  Perhaps two questions could be made out of this.
It would seem that the main battle of the enemy is on truth in order to deceive the mind.
The Father of Distortion
In the Fall of Mankind, Satan's first statement was to question the truth of the Word of God.  He completely misquotes God, who did not say &quot;You shall not eat of any tree in the garden&quot; as he suggests, but actually said, &quot;You may surely eat of every tree of the garden...&quot; except one.  So, Satan distorts the Word of God in order to attack the character of God, making Him out to be prohibitive in nature when He is actually generous in nature.

Now the serpent was more crafty than any other beast of the field that the Lord God had made. He said to the woman, “Did God actually say, ‘You shall not eat of any tree in the garden’?”  Genesis 3:1 ESV
“You may surely eat of every tree of the garden, but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die.”  Genesis 2:16-17 ESV

The Father of Lies
Next, Satan asserts that there is no consequence to sin, and even asserts that sin will be to their benefit.  This is a complete lie, of course.  The truth is that there most certainly would be a consequence to sin.

But the serpent said to the woman, “You will not surely die. For God knows that when you eat of it your eyes will be opened, and you will be like God, knowing good and evil.”  Genesis 3:4-5 ESV

The Deception of the Mind
After this, the woman's mind was completely deceived, and it was at that point that she sinned against God.

So when the woman saw that the tree was good for food, and that it was a delight to the eyes, and that the tree was to be desired to make one wise, she took of its fruit and ate, and she also gave some to her husband who was with her, and he ate.

Conclusion
So, Satan's tactic was to deceive the woman.  She believed that God was not as good as she had thought He was.  She believed that there would be no consequence to sin.  She believed that God was withholding something good from her, and that she would actually gain from sin.
Satan is also called &quot;the father of lies&quot; (John 8:44) and &quot;the Deceiver&quot; (Revelation 12:9).  So, distorting the truth in order to deceive the mind is certainly a primary focus of his.
That makes Jesus' prayer in John 17 all the more instructive, that we are sanctified by the truth, and the Word of God is truth.  (John 17:17)