Humor (spotting semi conscious truths that connect us, and make us laugh.) goes when the unconscious connection fades, and as its labido is repressed, it manifests the Trickster Archetype.
Anything worth thinking, or speaking is worth laughing about, or laughing at.
When you have lost the ability to laugh at yourself, or your ideas, you are inviting the Trickster into the objective reality.
One looses this ability when one takes themselves too seriously, pride in one’s self and lack of humility tend to do this.