What is mental warfare and how to combat it?

Isaiah 40:1-5 KJV

#Step [1] Comfort ye, comfort ye my people, saith your God. #Step [2] Speak ye comfortably to Jerusalem, and cry unto her, that her warfare is accomplished, that her iniquity is pardoned: for she hath received of the Lord's hand double for all her sins. [3] The voice of him that crieth in the wilderness, Prepare ye the way of the Lord, make straight in the desert a highway for our God. [4] Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places plain: [5] And the glory of the Lord shall be revealed, and all flesh shall see it together: for the mouth of the Lord hath spoken it.

2 Corinthians 10:4-6 KJV

[4] (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;) [5] Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ; [6] And having in a readiness to revenge all disobedience, when your obedience is fulfilled.

1 Timothy 1:18-20 KJV

[18] This charge I commit unto thee, son Timothy, according to the prophecies which went before on thee, that thou by them mightest war a good warfare; [19] Holding faith, and a good conscience; which some having put away concerning faith have made shipwreck: [20] Of whom is Hymenaeus and Alexander; whom I have delivered unto Satan, that they may learn not to blaspheme.

Proverbs 18:12-17 KJV

[12] Before destruction the heart of man is haughty, and before honour is humility. [13] He that answereth a matter before he heareth it, it is folly and shame unto him. [14] The spirit of a man will sustain his infirmity; but a wounded spirit who can bear? [15] The heart of the prudent getteth knowledge; and the ear of the wise seeketh knowledge. [16] A man's gift maketh room for him, and bringeth him before great men. [17] He that is first in his own cause seemeth just; but his neighbour cometh and searcheth him.