About the nervous system's four survival strategies There are reactions we call overreactions . But the body doesn't know that word. The body only knows one task: to protect you . When the nervous system experiences danger – real or perceived – it does not choose to act intentionally. It chooses what once worked. Struggle – when the body says: I must stand firm The fight-or-flight response occurs when the system assesses that there is still enough energy to defend itself.