A cheerful mind.

It is useless today to even refute the claim circulated. At the last century’s end, of a “joyful antiquity” and a sad Christianity. The early success of Christianity, the religion of the poor and uneducated, in the cultural world of the Roman Empire, can also be explained by the fact that it promised victory over everything against which man felt powerless: fate, death, pain.
The proclamation of the doctrine of Christ was given the name eu-Evangelion – the good, glad tidings. Christianity is a religion of grace. The Greek word chara means joy. We translate the angel’s greeting to Mary as “Hail Mary.” The Greek chair is literally “Rejoice!” (Old English liturgical texts have the expression “Rejoice!”)
Scripture encourages prayer with a sense of joy (cf. Ps 31:11; 9:5; 99:1; 104:3, etc.). We are often reminded of the words of St. Paul: “Not out of grief nor out of compulsion, for God loves a cheerful giver” (2 Cor 9:7). The culmination and goal of Christian perfection is love. Whoever loves, gives gladly, even with sacrifice, speaks gladly to the one he loves. He who prays and joyfully denies proves that he does his duty out of love. The work which we do joyfully goes, as it were of itself a hand. Aristotle writes: “Joy perfects the work, sorrow destroys it”. St. John Chrysostom explains in this sense the verse of the Psalm (118,32): ‘I will run in the way of thy commandments. Joy gives strength, and strength gives freshness. Everything goes much easier and faster. He who has a joyful attitude towards life, the little, and overcomes great ones with courage.

We are not worried about his future. On the contrary, if we see someone permanently sad, we rightly fear that he will not last on the path he has started, especially if there are major difficulties. The joyful performance of religious duties is an effective way of apostolate. It does not attract the company of sad people and discontented; on the contrary, all would like to go where they see, that there is happiness and joy. St. Leo exhorts the religious to their “modesty to be holy and not sad”. St. Francis wished to see a joyful countenance on his brothers, a desire to do more than they have been doing, and not weariness and weariness. That is how they are to go out into the streets. Christian morality teaches that a virtuous life is a life according to God and according to a happy and innocent nature,  as it came from the hands of the Creator. Whoever strives for virtue and is in doing so joyless, denies the truth he wants to believe. At least, the impression he gives to others.
Hence Hermas (2d cent.) ranks sorrow among the evil desires which are to be banished from the heart. The only praiseworthy sorrow, as the Ascetics uniformly teach, is regret for sin. This, however, soon becomes the source of true joy. As his biography tells us, St. Francis of Assisi warned against sorrow. The sorrow of man is the joy of the devil. A sad man is easily led to despair or to seek illicit pleasures in the world. This is in agreement with what St. Gregory the Great wrote:
“The soul cannot be without pleasure, so it seeks pleasure in low things if it has none in things noble.”