The quote "If a bird flies straight at you, prepare for a bad day" from Kelley Armstrong's book "Omens" suggests that sometimes unexpected or unusual signs can indicate trouble ahead. It highlights the idea that when faced with an ominous sign, one should be wary and prepare for potential challenges. The metaphor of a bird symbolizes unexpected events that can disrupt one's day or lead to unforeseen consequences.

This piece of wisdom reflects a broader theme in literature where omens or warnings serve as harbingers for things to come. The notion encourages individuals to be alert and considerate of the signs around them, reminding readers to take heed of their intuition and circumstances, especially when things seem out of the ordinary.