I take my relationship with Christ seriously. But it's the kind of "seriousness" that children exhibit when they play. Intensity and absorption mingled with abandonment and joy. As G.K. Chesterton said, "It is the test of a good religion whether you can joke about it."
There is a kind of "seriousness" that is poison. It leads to legalism and even depression. That was the problem the pharisees had. They were so uptight that they served God out of duty rather than love.
This "tainted seriousness" is not just found in religion, but also in politics and everyday living. Rigidness is one manifestation. Another is to believe that things are actually as bad as you imagine they are.
So what's the antidote? One is to just lighten up. Another is to exaggerate circumstances until they are so ridiculous that you can't help but laugh. St. Francis of Asissi was good at this as exemplified in a conversation he had with friar while walking in a cold winter storm:
"When we come to St. Mary of the Angels (monastery) soaked by the rain and frozen by the cold, all soiled with mud and suffering from hunger, and we ring at the gate of the place and the brother porter comes out and says angrily: 'Who are you?' and we say: 'We are two of your brothers.' And he contradicts us, saying, 'You are not telling the truth. Rather you are two rascals who go around deceiving people and stealing what they give to the poor. Go away!' And he does not open for us, but makes us stand outside in the snow and rain, cold and hungry, until night falls--then if we endure all those insults and cruel rebuffs patiently, without being troubled and without complaining, and if we reflect humbly and charitably that the porter really knows us and that God makes him speak against us, oh, Brother Leo, write that perfect joy is there."
By imagining such an extreme scenario, he could walk in the snow and rain with joy rather than complaint and despair. Plus, even if such a thing happened, he was already prepared to be joyful.
Jesus offered the cure of exaggeration to the pharisees. They were blind to justice, mercy, and faith because of their "seriousness". Our Lord said that they "strain out a gnat and swallow a camel!" (Matthew 23:24). What an absurd image, but it showed how ridiculous their legalism was. Then he continued with images of cups that are clean on the outside but filled with filth, of whitewashed tombs that contain decaying bodies.
Take the horrendous tragedies in your life and look at them in a way that will make you laugh. If you are taking life too seriously, have a bowl of camel soup.