11 Having heard this, direct your heart to Godward. Do not deceive yourselves. Ask yourselves then when it is well with you in the world; then ask yourselves, whether ye love the world, or whether ye love it not; learn to let it go before you are let go yourselves. What is to let it go? Not heartily to love it. Whilst there is yet something with you which you must one day lose, and either in life or death let it go, it cannot be with you always; while I say it is yet with you, loosen your love; be prepared for the will of God, hang upon God.
Hold you fast to Him, whom you can not lose against your will, that if it chance you to lose these temporal things, you may say, “The Lord gave, the Lord has taken away, as it has pleased the Lord, so is it done, blessed be the Name of the Lord.” But if it chance, and God so wills it, that the things you have be with you even to the last: for your detachment from this life you receive the denarius, the fifty, and the perfection of blessedness comes to pass in you, when you shall sing Hallelujah.
Having these things which I have now brought forward in your memory, may they avail to overthrowing your love of the world. Evil is its friendship, deceitful, it makes a man the enemy of God. Soon, in one single temptation, a man offends God, and becomes His enemy. Nay not then becomes His enemy; but is then discovered to have been His enemy. For when he was loving and praising Him, he was an enemy; but he neither knew it himself, nor did others. Temptation came, the pulse is touched, and the fever discovered.
So then brethren, the love of the world, and the friendship of the world, make men the enemies of God. And it does not make good what it promises, it is a liar, and deceives. Therefore men never cease hoping in this world, and who attains to all he hopes for? But whereunto soever he attains, what he has attained to is immediately disesteemed by him. Other things begin to be desired, other fond things are hoped for; and when they come, whatsoever it is that comes to you, is disesteemed.
Hold you fast then to God, for He can never be of light esteem, for nothing is more beautiful than He. For for this cause are these things disesteemed, because they cannot stand, because they are not what He is. For nought, O soul, suffices you, save He who created you. Whatsoever else you apprehend is wretched; for He Alone can suffice you who made you after His Own likeness. Thus it was expressly said, “Lord, show us the Father, and it suffices us.” There only can there be security; and where security can be, there in a certain sort will be insatiable satiety. For you will neither be so satiated, as to wish to depart; nor will anything be wanting, as though you could suffer want.
Source: Sermons on Selected Lessons of the New Testament (New Advent)