WHAT IS USEFUL 

First, we have seen what is virtuous and seemly. Now let us see what is useful in acquiring holiness. In Scriptures, what is virtuous is also useful: "All things are lawful unto me, but all things are not profitable (i.e. useful)."

Man sins; this is not virtuous nor seemly. To live in sin is easy but it is not right. What is useful is also just. And it is both useful and just to serve Christ and to give up oneself, even unto death to serve Him. To avoid death, therefore, is unjust. We must choose the useful that is full of virtues, for what is virtuous is useful and what is useful is virtuous. Also, what is useful is just and what is just is useful. 

People wrongly equate useful to whatever smacks of material profit in the pursuit of money. But true usefulness contains precisely the element of losing earthly possessions "that we may gain Christ." Useful is that which leads us to Godliness with contentment.

There is a usefulness connected with the body and one directed with the soul "Bodily exercises profiteth little, but Godliness is profitable unto all things." What is useful? Integrity, to preserve one's body unspotted and undefiled, that a widow remain as she is, that one attains holiness and the salvation of one's soul. 

St. Ambrose: Christian Priesthood,  Book II, Chapter 6

(04-04-03)