"Be anxious" is a present tense imperative calling for a lifestyle in which one makes the daily (yea, even moment by moment) choice (active voice calls for a decision of one's will) empowered, controlled, nudged and stimulated by the Holy Spirit [e.g., Ro8:13] and enabled by God's grace [Php 2:13]) to not be anxious in circumstances that would otherwise be expected to produce anxiety in any natural man or woman (we are natural people with a supernatural power which the world needs to see worked out in real life situations!)

"Be anxious" (Verb form merimnao from  the noun mérimna = anxious care in turn from merís = part and merizo = to divide or draw different directions - which is exactly what anxiety does to most of us!) means to have an anxious concern, based on apprehension about possible danger or misfortune and is characterized by extreme uneasiness of mind or brooding fear about some contingency and emphasizes fear of frustration, failure or disappointment.  Worry means to be pulled in different directions. Our hopes pull us in one direction; our fears pull us the opposite direction; and we are pulled apart! The English word "anxious" has a very "telling" derivation from the Latin word Latin anxius which is akin to Latin angere which means to strangle! Isn't that what anxiety does to most of us...strangle us and render us almost totally ineffective in God's kingdom work?!

Wiersbe comments that "From the spiritual point of view, worry is wrong thinking (the mind) and wrong feeling (the heart) about circumstances, people, and things. Worry is the greatest thief of joy. It is not enough for us, however, to tell ourselves to “quit worrying” because that will never capture the thief. Worry is an “inside job,” and it takes more than good intentions to get the victory. The antidote to worry is the secure mind: “And the peace of God... shall keep [garrison, guard like a soldier] your hearts and minds through Christ Jesus” (Phil. 4:7). When you have the secure mind, the peace of God guards you (Phil. 4:7) and the God of peace guides you (Phil. 4:9). With that kind of protection—why worry?"

The NT realizes that life is swayed by care. Concern is unavoidable but it is given a new orientation. Liberation from it comes as one casts it upon God. How do we "cast" our burdens upon God? Somewhat paradoxically by continually making our anxieties known to Him Who already knows all -- it seems that even though God obviously knows, our very act of declaring our prayers & needs to Him is a humbling of one's self beneath His mighty hand...His hand which lifts up the brokenhearted (Ps34:18), the downcast...see gnorizo below.

Prayer grants freedom from care, no matter how He answers...He hears all & He always answers in His will in a way that causes all things to work together for good, for our growth & ultimately for His glory. Hallelujah. What an awesome all-wise God we worship.

Spurgeon wrote "There is no more blessed way of living than a life of dependence upon a covenant-keeping God. We have no care, for he careth for us; we have no troubles, because we cast our burdens upon the Lord."

Edward Everett Hale (1822-1909), former US Senate chaplain, said, "Never attempt to bear more than one kind of trouble at once. Some people bear three kinds--all they have had, all they have now, and all they expect to have."

"Nothing" is the Greek word medeis which literally means "not even ONE thing"! And not surprisingly this phrase is first in the Greek construction for emphasis...let us lay hold of the Father's will (NOT ONE THING) by the Spirit's power through the grace in Jesus Christ that flows from His throne.

"Careful for nothing, prayerful for everything, thankful for anything". Dwight Lyman Moody (1837-1899)

BUT IN EVERYTHING BY PRAYER AND SUPPLICATION: all en panti te proseuche kai te deesei : (Genesis 32:7-12; 1 Sa1:15; 30:6; 2 Chr32:20; 33:12,13; Ps34:5-7; 51:15; Ps55:17,22; 62:8; Pr3:5,6; 16:3; Jer33:3; Mt:7,8; Luke 18:1,7; Lu12:22; Eph6:18; Col4:2; 1 Th5:17,18; 1 Pe 4:7; Jude20,21) (See John Macarthur's exposition on Php4:5-7 & Php4:6-8  and  4:6b-7Thankful Prayer)

"Prayer" (proseuche) refers to prayers to God and conveys the ideas of adoration, devotion, and worship. Paul's point then is the first priority when we find ourselves worrying, should be to get alone with God to adore Him, focusing on  His greatness and majesty. Then the God Who may have seemed to "small" or too "indifferent" to our plight, begins to be envisioned as big enough to handle all of our problems. If you are like me, too often we rush into His presence, blurting out our needs, when we should be adoringly approaching His throne of grace with a sense of deepest reverence. And so the first thing Paul instructs the saint to do in prayer is focus on God's character. A fruitful discipline is to praise Him for His many names (click here) or His changeless attributes (click here). (See the note below on "Like a River Glorious")

Prayer = to look at the character of God. Supplication = specific requests. Thanksgiving = our attitude (1Th5:18) What is the result of seeing His character, specifically asking Him & finally giving thanks for your circumstances? PEACE! (4:7) When we begin to become anxious (knowing that anxiety often causes FEAR), we are to go to God in prayer & supplication with thankful hearts.

We are to worry about nothing because we can pray about everything.

"Supplication" (deesis) refers to prayers from a perspective of NEED. We are all paupers and in need of His daily grace: Give us this day our daily bread!

WITH THANKSGIVING LET YOUR REQUESTS BE MADE KNOWN TO GOD: meta eucharistias ta aitemata humonon gnorizestho (3SPPM) pros ton theon: (1 Sa7:12; 2 Co1:11; Ep5:20; Col3:15,17) (Spurgeon on Prayer Perfumed with Praise) (Pr15:8; Song2:14; Mt6:8)

"Thanksgiving" (eucharista) implies gratitude and also perfect submission to the will of God. It is only when we are fully convinced that God is working all things together for good that we can really give to Him the perfect gratitude which believing prayer demands.

When we are justified by faith we are given peace with God (Ro5:1) Set at one again (like Eden) , opposite of war or disturbance (before salvation or when walking in darkness we are ''at war'' with the Almighty and our peace with Him is ''disturbed'' by His Holy Spirit. Confession & Repentance brings Reconciliation & Restoration). The peace of God is a sense of holy repose and complacency which floods the soul of the believer when he is leaning hard upon God.  Frances Ridley Havergal conveyed this truth beautifully in the words of the hymn Like a River Glorious...

WHICH SURPASSES ALL COMPREHENSION: e huperechousa (PAPFSN) panta noun: (Ep3:19; Rev2:17)

God's peace CONTINUALLY STANDS OUT & IS SUPERIOR & is more EXCELLING than the world's peace or any so called peace we might be able to well up because of ''positive thinking'' etc.
 

It is beyond our ability to produce it by our own intellect.

A person whose cancer has been arrested may say, “I am so thankful to God.” That is praise. But a person who is dying of cancer and in pain may calmly say, “Everything is all right. The Lord doesn’t make mistakes. I have peace in my heart.” That is “the peace that passes all understanding.”

SHALL GUARD YOUR HEARTS AND MINDS IN CHRIST JESUS: phrouresei (3SFAI)  tas kardias humon kai ta noemata humon en Christo Iesou: (Neh8:10; Pr2:11; 4:6; 6:22) (Spurgeon on How to Guard the Heart)  (1 P1:4,5; Jude 1:1)