Thomas a Kempis — We must be watchful…

We must be watchful, especially in the beginning of the temptation.  The enemy is then more easily overcome, if he is not permitted in any wise to enter the door of our hearts, but is resisted without the gate at his first knock…First there comes to the mind a bare thought of evil, then a strong imagination thereof, afterward delight, and an evil motion, and then consent.  And so little by little our wicked enemy gets complete entrance, because he is not resisted in the beginning.  And the longer a man is slow to resist, so much the weaker does he become daily in himself, and the enemy stronger against him.
Thomas a Kempis