It was once announced that the Devil was going out of business and would offer his tools for sale to whoever would pay his price.
On the night of the sale they were all attractively displayed and a bad looking lot they were.
Malice, envy, hatred, jealousy, sensuality, deceit and the other implements of evil were spread out, each marked with its price.
Apart from the rest lay a harmless looking wedge-shaped tool, much worn and priced higher than any of the others.
Someone asked the Devil what it was. "That's discouragement," was the reply.
"Well, why do you have it priced so high?"
"Because," replied the Devil, "it is more useful than any of the others.
I can pry open and get inside a person's consciousness with that when I couldn't get near them with any of the others.
Once inside I can use them in whatever way suits me best.
It is so worn because I use it with nearly everybody, as very few people yet know that it belongs to me."
While simply a fable, there is a lot of truth in that story. That's why God included in his instructions to Joshua to "not be discouraged".
We are also challenged to watch out for each other in this battle of sin so "that none of you has a sinful, unbelieving heart that turns away from the living God. But encourage one another daily… so that none of you may be hardened by sin's deceitfulness" - Hebrews 3: 12-13, emphasis added.