The meanest of sins is the most secret - jealousy. Yet secret though it be, hidden so that none may suspect its presence, it works terrible poison in life. The very secrecy itself helps this along, for we are ashamed of so ungenerous a feeling and have no desire to take others into our confidence about it. Occasionally, indeed, our feelings may be too much for us, and a broken expression, snapt out in a moment of provocation, may easily tell what has long lain silent in our minds; the sudden outbreak of war reveals the unguessed secret thoughts of many hearts. Still, the attempt to prevent others suspecting us of so mean a sin drives the poison deeper into the blood: it works a veritable fever. Perhaps if we would only talk, air our grievances, say precisely what we feel, the pent-up and restrained antagonism would be swept away and the animosity at least temporarily relieved. But no, in silence we nurse our hatred of another's success. We have worked earlier, longer, more successfully, but the other is chosen. We have squandered our affection, done everything in our power to ease and help those whom we love intensely, yet the other is chosen and we are left. They have had advantages denied to us, yet in spite of it no allowance is made for our more determined efforts. They succeed and we are failures, and such a judgement suffices for the world. Or even at times the very fact of their great deserts does not mitigate, but rather increases, our jealousy; and the knowledge that we have failed, because of our own fault, very often makes our hatred the more unforgiving.
But it is also necessary to remember that the sin of jealousy is not the mere desire for equal success with another. We are jealous when we wish to be or do what others are or do, and wish at the same time that they themselves were deprived of their accomplishment. I cannot help contrasting my own poverty or want of decent livelihood with the luxury and possessions of better folk; nor, again, can I help wishing that this gift of nature or grace were mine - their charm or gracefulness or physical strength or good looks. Again, the man who is discontented with his lot, and, fired by ambition, aims at achieving a higher position for himself and his children, can hardly be called a sinner; and when I myself am so stirred by others success as to venture into rivalry with them and attempt to oust them by fair competition from their place of supremacy, and to develop my own artistic or scientific skill which I know to be superior to theirs, am I in all these ways following after sin? Certainly not. In the case of one who attempts by fair competition to drive out a rival, he is simply putting to use the powers God gave him. But in this the whole trouble is the motive of my action. If it be simply that I wish to have what they have, this is not sinful, nor is it jealousy in the ordinary meaning of the word; but if I wish deliberately to deprive them of what they have already got, and am pleased at the thought of contrasting my possession with their loss, then that is indeed jealousy. The sin, therefore, consists in the secret dislike of other people's enjoying what I would wish to be exclusively my own.
Jealousy, however, is not merely a sin; it is also a blunder. Just as pride is foolish since it puffs up a man with self-glorification over deeds that are none of his own, so jealousy in much the same spirit makes us greedy of the works, not of man, but of God. When I am tempted to think much of myself because of some wonderful thing I have done, I answer myself by saying that after all I was but an instrument in the hands of God; to Him alone is due the glory of the thing. In the same fashion, when I am jealous of another's achievement let me remember that they, no less than I, owe their success to God. The foolishness, therefore, of jealousy should very easily move me. Once I am convinced that others are no more to be praised for what they have done well than am I for my great deeds, then jealousy can no longer affect me. Truth would drive me to admit the excellence of their accomplishment, but to trace back that excellence to no human origin, but Divine; and when I find that others are preferred to me for posts of importance and, above all, are higher in the friendship of those whose love is, to me, the most precious thing on earth, I must remember that the same indignity was set upon my Master. Whatever advantage, then, others have over me has to be traced to God's greater condescension to them. They possess more than I do, but that is simply that they have borrowed more plumage than I have. And when, in spite of all this, I feel the pangs of being set aside, let me remember how another was preferred to Christ; "and Barabbas was a robber." In memory, then, of His patience let my jealousy be healed.
- text taken from by Father Bede Jarrett, O.P.