More from St. Catherine of Siena's letter to Lorenzo del Pino, in which she addresses the question of how a Christian might live in the world:
A man can hold to riches and worldly place if he likes, and he does not wrong God nor his own soul; but it would be greater perfection if he renounced them, because there is more perfection in renunciation than in possession. If he does not wish to renounce them in deed, he ought to renounce and abandon them with holy desire, and not to place his chief affections upon them, but upon God alone; and let him keep these things to serve his own needs and those of his family, like a thing that is lent and not like his own. So doing, he will never suffer pain from any created thing; for a thing that is not possessed with love is never lost with sorrow...
[All things] should be possessed with moderation in the light of reason, loved in such wise as they should be loved. And he who holds them thus will not hold them with the help of sin, but with grace; with generosity of heart, and not with avarice; in pity for the poor, and not in cruelty; in humility, not in pride; in gratitude, not in ingratitude: and will recognize that his possessions come from his Creator, and not himself.
So there you have it, Dr. Benincasa's prescription to avoid wronging God or your soul through your possessions.
No wonder it's easier for a camel to pass through the eye of a needle.