The turtle had jerked into its shell, but now it hurried on, for the highway was burning hot.
– John Steinbeck
The Grapes of Wrath, Chapter 3. When the woman driver swing to the right to avoid the turtle, it first retreats into the safety of its shell. This is because of the instinct to survive and protect itself from life’s difficulties. But then it gathers courage and decides to persevere on across the burning hot highway.