Ignoring comets
I suppose that when you cross the street you only look for cars, and ignore the trucks...
It's very easy to adopt mental defense mechanisms, while it's quite difficult to face up to bad news.
The observed historical rates for impacts are around 1 Tunguska class per 100 years, 1 mega-tsunami per 1,000 years, and 1 extinction level event per 26,000,000 years.
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