There are both dark and light sides to this topic. Some Church Fathers condemn it because in all seriousness, trying to work out our salvation isn't a laughing matter and we have nothing to laugh about when living a life of repentance. Others say it can be used against us in the unseen warfare, because the devil see's and hears everything. Others say it can be a good thing, but don't do so much of it. There are many ways to working out our salvation, we are all different and we each need our own help, some more than others.
I like the story of Saint Anthony and the wandering hunter with the bow.
"A hunter, wandering through the desert, came upon Abba Anthony while he was making jokes with the brethren; and he was shocked. Wishing to teach the hunter that it is sometimes necessary to relax with the brethren, the old man said to him: “Put an arrow in your bow and bend it.” The hunter did so. “Bend it a little more,” said Anthony. The hunter obeyed. “And still more,” Anthony told him. “But if I draw the string too tight,” said the hunter, “the bow will snap.” And the old man said to him: “It is the same in the work of God. If in the case of the brethren we draw the string too tight, they will snap under the strain. So it is necessary sometimes to relax with them.” When the hunter heard this, he was filled with compunction, and profiting much from what the old man had said, he went his way. And the brethren, greatly strengthened, departed to their own place."
Humor can be good, I have a friend here in town who is a monk from Mt Athos, he spent 10 years their and his mission here is to start a Russian Mission Church and Skete. He is living in the woods and there is a baby deer who's mother was killed. Humans raised the deer so it'll run up to you like a dog. My monk friend laughs and jokes about wanting to put on his vestments and hand feed the deer, take a picture and send it to his friends on Mt Athos saying "look, wild animals are already coming to me, I'm already a Saint" whilst joking laughing about how silly the idea is, joking can be okay.