God certainly has a plan for everything. Every step we take, every breath we breathe, every decision we make, he has known before us. He gives us the freedom and the free will to run our own lives. He simply set forth some parameters for us in the beginning.
In this text the Bible refers to a city whose walls have been broken down, and is left vulnerable to invaders. Our lives are the same way. When we lack the self control, when we allow the walls made of our values to fall, we allow the devil into our lives. At first it may be only one or two mistakes, but eventually our life is overrun and taken over by Satan, and only through God's grace are we rescued.
I pray today that God will strengthen my walls of self control and keep his hand upon me, guiding me through life with gentle reminders of the rules he set forth. And I pray that he will give me the strength to stare down temptation and live to glorify him in every way.