NullReferenceException: Object reference not set to an instance of an object

is there anything wrong with line 11, and 18? NullReferenceException: Object reference not set to an instance of an object

 #pragma strict
 
 private var mBlur : MotionBlur;
 
 private var sanityScript : SanityManager;
 
 function Start()
 {
     mBlur = GameObject.Find("Main Camera").GetComponent(MotionBlur);
     sanityScript = GameObject.Find("First Person Controller").GetComponent(SanityManager); 
     mBlur.enabled = false;
     
 }
 
 function Update()
 {
     if(sanityScript.currentSanity >= 20)
     {
         mBlur.enabled = true;
         mBlur.blurAmount = 0.6f;
     }
     
     if(sanityScript.currentSanity >= 40)
     {
         mBlur.enabled = true;
         mBlur.blurAmount = 0.8f;
     }
     
     if(sanityScript.currentSanity >= 60)
     {
         mBlur.enabled = true;
         mBlur.blurAmount = 1.0f;
     }
     
     if(sanityScript.currentSanity >= 80)
     {
         mBlur.enabled = true;
         mBlur.blurAmount = 1.3f;
     }
     
         if(sanityScript.currentSanity >= 90)
     {
         mBlur.enabled = true;
         mBlur.blurAmount = 1.6f;
     }
 }