The higher one's source is, the further it can fall.
Falling into Machshovois Zorois, and all the Tumah it leads to, is just one side of the coin. 
The lower one falls, the higher the potential for Machshovos Toivois and Tahara. 
The Yetzer Hora is freaked out by the potential of this success, and fights strongly to make a person fall repeatedly, and have feelings that he does not know if he will ever succeed. 
It's a false trick. 
If the Rebboinoi Shel Oilom gives us back our Neshomois each morning, then we then He Knows that we Can succeed, and we so we must never give up.