For there are two loves from which proceed all wishes, as different in quality as they are different in their sources. For the reasonable soul, which cannot exist without love, is the lover either of God or the world. In the love of God there is no excess, but in the love of the world all is hurtful. And therefore we must cling inseparably to eternal treasures, but things temporal we must use like passers-by, that as we are sojourners hastening to return to our own land, all the good things of this world which meet us may be as aids on the way, not snares to detain us. Therefore the blessed Apostle makes this proclamation, the time is short: it remains that those who have wives be as though they had none; and those who weep, as though they wept not; and those who rejoice, as though they rejoiced not; and those who buy, as though they possessed not; and those that use this world, as though they used it not. For the fashion of this world passes away. But as the world attracts us with its appearance, and abundance and variety, it is not easy to turn away from it unless in the beauty of things visible the Creator rather than the creature is loved; for, when He says, you shall love the Lord your God from all your heart, and from all your mind, and from all your strength, He wishes us in [no way] to loosen ourselves from the bonds of His love. And when He links the love of our neighbour also to this command, He enjoins on us the imitation of His own goodness, that we should love what He loves and do what He does.
Leo I, Sermon 90. (The words I've substituted in square brackets are certainly the correct phrase, rather than 'noticing', which seems to be a typo.)