Your life, beloved, is a war and temptation precipitates each battle. 

Saint Theophan the Recluse said it this way: “The arena, the field of battle, the site where the fight actually takes place is our own heart and all our inner man. The time of battle is our whole life.” 

St. James tells us that every man is tempted from within, being lured away by his own lusts and passions, and is enticed.  (James 1:14)

In Mark 7, our Lord says this:

“Hear Me, everyone, and understand: There is nothing that enters a man from outside which can defile him; but the things which come out of him, those are the things that defile a man.”