The psychological phases of those involved in bubbles.
We all go through emotional phases:
This can result in rationalization when a person is presented with evidence of a bad choice, or in other cases. Prevention of cognitive dissonance may also contribute to confirmation bias or denial of discomforting evidence. If not corrected, this can lead to further bad choices for the sake of consistency, rather than learning from mistakes.
The Stages of Grief
When prices first drop and the market enters the denial stage, the individual market participants feel confusion and attempt to avoid the truth. This is motivated by fear they may have been wrong to purchase when they did, and they might lose money. They seek ways to quell these fears through drinking even more kool aid. Bulls in the denial stage will not come to a blog like this one because we will not feed their denial. Some will stop by, try to convince us we are wrong, and move on. The only person they are really trying to convince is themselves.
From this comprehensive article on bubble psychology: