Luke 10:19

Listen carefully: I have given you authority (that you now possess) to tread on serpents and scorpions, and (the ability to exercise authority) over all the power of the enemy (Satan); and nothing will (in any way) harm you. 

Christians must recognize the authority Jesus gave here on earth and walk in it. WE are to tread on sickness, lack, depression, and use our authority to remove them from our lives. Whatever the enemy tries to insinuate into our minds, WE are to cast out and cast down by using the word. Nothing will (in any way) harm you when we take a stand against the enemy in the Name of Jesus.