Objection 1. It would seem that sorrow is not a virtuous good. For that which leads to hell is not a virtuous good. But, as Augustine says (Gen. ad lit. xii, 33), "Jacob seems to have feared lest he should be troubled overmuch by sorrow, and so, instead of entering into the rest of the blessed, be consigned to the hell of sinners." Therefore sorrow is not a virtuous good.
Objection 2. Further, the virtuous good is praiseworthy and meritorious. But sorrow lessens praise or merit: for the Apostle says (2 Corinthians 9:7): "Everyone, as he hath determined in his heart, not with sadness, or of necessity." Therefore sorrow is not a virtuous good.
Objection 3. Further, as Augustine says (De Civ. Dei xiv, 15), "sorrow is concerned about those things which happen against our will." But not to will those things which are actually taking place, is to have a will opposed to the decree of God, to Whose providence whatever is done is subject. Since, then, conformity of the human to the Divine will is a condition of the rectitude of the will, as stated above (Question 19, Article 9), it seems that sorrow is incompatible with rectitude of the will, and that consequently it is not virtuous.
On the contrary, Whatever merits the reward of eternal life is virtuous. But such is sorrow; as is evident from Matthew 5:5: "Blessed are they that mourn, for they shall be comforted." Therefore sorrow is a virtuous good.
I answer that, In so far as sorrow is good, it can be a virtuous good. For it has been said above (Article 1) that sorrow is a good inasmuch as it denotes perception and rejection of evil. These two things, as regards bodily pain, are a proof of the goodness of nature, to which it is due that the senses perceive, and that nature shuns, the harmful thing that causes pain. As regards interior sorrow, perception of the evil is sometimes due to a right judgment of reason; while the rejection of the evil is the act of the will, well disposed and detesting that evil. Now every virtuous good results from these two things, the rectitude of the reason and the will. Wherefore it is evident that sorrow may be a virtuous good.
Reply to Objection 1. All the passions of the soul should be regulated according to the rule of reason, which is the root of the virtuous good; but excessive sorrow, of which Augustine is speaking, oversteps this rule, and therefore it fails to be a virtuous good.
Reply to Objection 2. Just as sorrow for an evil arises from a right will and reason, which detest the evil, so sorrow for a good is due to a perverse reason and will, which detest the good. Consequently such sorrow is an obstacle to the praise and merit of the virtuous good; for instance, when a man gives an alms sorrowfully.
Reply to Objection 3. Some things do actually happen, not because God wills, but because He permits them to happen--such as sins. Consequently a will that is opposed to sin, whether in oneself or in another, is not discordant from the Divine will. Penal evils happen actually, even by God's will. But it is not necessary for the rectitude of his will, that man should will them in themselves: but only that he should not revolt against the order of Divine justice, as stated above (Question 19, Article 10).
Source: Summa Theologica (New Advent)