As a follower of Christ, battle is inevitable.
We can't go into battle unarmed.
For though we walk in the flesh, we do not war after the flesh: (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;) Casting down imaginations, and ever high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;
2 Corinthians 10:3-5    (Carnal: translated from the Greek word sarkikos, which literally means "fleshly")

We have to know who we're battling.
For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places. Ephesians 6:12

Most importantly, we have to obey our Commander.
We are commanded to STAND,
while we use our armor and our weapon of prayer. 

 Wherefore take unto you the whole armour of God, that ye may be able to withstand in the evil day, and having done all, to stand. Stand therefore, having your loins girt about with TRUTH, and having on the BREASTPLATE of RIGHTEOUSNESS; And your feet shod with the PREPARATION OF THE GOSPEL of PEACE; Above all, taking the SHIELD OF FAITH, wherewith ye shall be able to quench all the fiery darts of the wicked. And take the HELMET OF SALVATION, and the SWORD of the SPIRIT, which is the word of God: PRAYING ALWAYS with all prayer and supplication in the Spirit, and WATCHING thereunto with all perseverance and supplication for all saints;
Ephesians 6:13-18

This battle can't be fought with worldly understanding. Although we are in the battle, we don't do the actual fighting.

God reassures us that He is in control.
Thus saith the Lord unto you, Be not afraid nor dismayed by reason of this great multitude; for the battle is not yours, but God's
2 Chronicles 20:15b

Right after that He tells Jehoshaphat to "go ye down against them," and goes on to say...

Ye shall not need to fight in this battle: set yourselves, stand ye still, and see the salvation of the Lord with you, O Judah and Jerusalem: fear not, not be dismayed; to morrow go out against them: for the Lord will be with you. 
2 Chronicles 20:17

Again, we see the command to STAND. We also see two more weapons for our use in battle.

And Jehoshaphat bowed his head with his face to the ground: and all Judah and the inhabitants of Jerusalem fell before the Lord, worshipping the Lord. And the Levites, of the children of the Kohathites, and the children of the Korhites, stood up to praise the Lord God of Israel with a loud voice on high. 
2 Chronicles 20:18-19

What "great multitude" is coming strongly against you? Is the Lord instructing you to STAND FIRM in a battle today? Is the enemy attacking your mind? Does it feel like he is winning the battle by getting you to walk in the flesh and not in the Spirit?
Use your weapons: PRAYER, WORSHIP and PRAISE.

They activate the power of God to work on your behalf. (Continue reading 2 Chronicles 20, below, to see how).
Thank God, He did not leave us powerless in the battle against the enemy! Your Prayer, your Worship and your Praise in the midst of any trial will disrupt, cripple and destroy Satan's plans toward you. Satan's whole plan was to get Job to curse God.

But put forth thine hand now, and touch all that he hath, and he will curse thee to thy face.
Job 1:11

All these years later, his plan is the same for you.
Just remember, He is already defeated.

2 Chronicles 20

20 And they rose early in the morning, and went forth into the wilderness of Tekoa: and as they went forth, Jehoshaphat stood and said, Hear me, O Judah, and ye inhabitants of Jerusalem; Believe in the Lord your God, so shall ye be established; believe his prophets, so shall ye prosper.21 And when he had consulted with the people, he appointed singers unto the Lord, and that should praise the beauty of holiness, as they went out before the army, and to say, Praise the Lord; for his mercy endureth for ever.s
22 And when they began to sing and to praise, the Lord set ambushments against the children of Ammon, Moab, and mount Seir, which were come against Judah; and they were smitten.sss23 For the children of Ammon and Moab stood up against the inhabitants of mount Seir, utterly to slay and destroy them: and when they had made an end of the inhabitants of Seir, every one helped to destroy another.s24 And when Judah came toward the watch tower in the wilderness, they looked unto the multitude, and, behold, they were dead bodies fallen to the earth, and none escaped.s25 And when Jehoshaphat and his people came to take away the spoil of them, they found among them in abundance both riches with the dead bodies, and precious jewels, which they stripped off for themselves, more than they could carry away: and they were three days in gathering of the spoil, it was so much.
26 And on the fourth day they assembled themselves in the valley of Berachah; for there they blessed the Lord: therefore the name of the same place was called, The valley of Berachah, unto this day.s27 Then they returned, every man of Judah and Jerusalem, and Jehoshaphat in the forefront of them, to go again to Jerusalem with joy; for the Lord had made them to rejoice over their enemies.s28 And they came to Jerusalem with psalteries and harps and trumpets unto the house of the Lord.29 And the fear of God was on all the kingdoms of those countries, when they had heard that the Lord fought against the enemies of Israel.30 So the realm of Jehoshaphat was quiet: for his God gave him rest round about.