Life's uncanny (de)motivator
Life is designed to depress you, to make you feel miserable and die a looser. It is up to you to prove Life wrong (and thus embrace it). Those few that survived out of billions weren't the ones to get depressed because of a loss of a limb or a loved one. Yes, they would have been shit scared of sabretooth tigers, crocodiles and strange diseases. And yes - many survived, because they would spit "into the mouth of death".