Matthew 6:31-34; 7:9-11
 Therefore take no thought, saying, What shall we eat? or,
What shall we drink? or, Wherewithal shall we be clothed?
(For after all these things do the Gentiles seek:) for your heavenly
Father knoweth that ye have need of all these things. But
seek ye first the kingdom of God, and his righteousness; and all these
things shall be added unto you. Take therefore no thought
for the morrow: for the morrow shall take thought for the things of
itself. Sufficient unto the day is the evil thereof. Or what man is there of you, whom if his son ask bread, will
he give him a stone? Or if he ask a fish, will he give
him a serpent? If ye then, being evil, know how to give
good gifts unto your children, how much more shall your Father which is
in heaven give good things to them that ask him?
St. Augustine of Hippo (called by the Orthodox Church "The Blessed Augustine") said regarding seeking "first the Kingdom of God and His righteousness" in "Our Lord's Sermon on the Mount" Ch. 27 — 56.
"For in the case of those who are seeking first the kingdom of God and His righteousness, i.e. who are preferring this to all other things, so that for its sake they are seeking the other things, there ought not to remain behind the anxiety lest those things should fail which are necessary to this life for the sake of the kingdom of God. For He has said above, 'Your Father knowest that ye have need of all these things.' And therefore, when He had said, 'Seek ye first the kingdom of God and His righteousness,' He did not say, Then seek such things (although they are necessary), but He affirms, 'all these things shall be added unto you,' i.e. will follow, if ye seek the former, without any hindrance on your part: lest while ye seek such things, ye should be turned away from the other; or lest ye should set up two things to be aimed at, so as to seek both the kingdom of God for its own sake, and such necessaries: but these rather for the sake of that other; so shall they not be wanting to you. For ye cannot serve two masters, who seeks both the kingdom of God as a great good, and these temporal things."
A few thoughts from the Philokalia regarding the cares of this world…
St. Isaac says:
"Without freedom from cares do not expect to find light in your soul, nor peace and silence with your senses at large (Ch. 69.1)."
St. John of the Ladders says:
"A small hair worries the eye and a small care destroys silence, for silence means laying aside of all thoughts not bearing on the work of salvation, and renunciation of all cares, even for matters of good report. Nor will a man who has attained true silence worry about his body for He Who promised to care for it is not false." (Ch. 27, 51, 52)
In Volume 4 of the Philokalia, there is a section entitled "On the Practice of the Virtues: One Hundred Texts", (.13)
"To master the mundane will of the fallen self you have to fulfill three conditions. First, you have to overcome avarice by embracing the law of righteousness, which consists in merciful compassion for one's fellow beings; second, that is to say, through all-inclusive self-control; and, third, you have to prevail over your love of praise through sagacity and sound understanding, in other words through exact discrimination in things human and divine, trampling such love underfoot as something cloddish and worthless. All this you have to do until the mundane will is converted into the law of the spirit of life and liberated from domination by the law of the outer fallen self. Then you can say, 'I thank God that the law of the spirit of life has freed me from the law and dominion of death.'" (cf. Rom.8:2)