It is human failure. It is the enemy sowing tares in your field of endeavor. It is the deception in someone else near you who lost faith in God. The enemy tries to hurt us through other humans, just like he tried to hurt Job through an unbelieving wife. Your heavenly Father watches over you with an unwavering eye.
Every move is monitored.
Every tear is bottled. He identifies with your every pain. He feels every hurt. And He knows when you have been exposed to enough harassment from the enemy. He will not permit a trusting child of His to go under because of too much pain and agony of soul.