There is joy of the world, and there is joy of the Lord. The joy of the world destroys the soul, the joy of the lord is our strength. Saint Clement of Alexandria used to say that the Christian person must always be cheerful, because they are a member of the body of the Lord Jesus Christ.
According to one of the fathers in the second century called Hermes, moodiness, or sadness and despair, prevent prayers from ascending to heaven. When you are cheerful, and you trust in the Lord Jesus Christ, he will accept and hear your voice, and even listen to your heart before you even utter a word. Therefore do not be upset, and always be cheerful.
the Holy Spirit is a source of joy, and when you are upset or in despair, the Holy Spirit cannot reside in your heart. Saint philexenos, said, when there is despair, and not cheerfulness, all demons will enter in the heart. This is serious and dangerous. As a Christian person, as an icon of the Lord Jesus Christ, we have to make sure heaven is in our heart.
“Be cautious of the tyrant of moodiness because it is a terrible being and a bad sadness, therefore we have to always be cheerful.”
– Saint John Chrysostom