Ki Seitzei

This parsha contains more commandments than any other. One commandment states, כי תבנה בית חדש , when you build a new house,ועשית מעקה לגגך, you must put a gate around the roof.  
The Ben Ish Chai has a very interesting take on this Posuk.
‎The clever person is never standing still; his thoughts are always full of new ideas & plans - whether it be materialistic, how he's going to succeed in business, or in spiritual matters, how much he plans on accomplishing in Torah. However, when those plans don't come to fruition, a person can become depressed. Even though the ideas were great when he started, the shattering of his dream can bring him all the way down. 

The Ben Ish Chai continues that even if a person on Rosh Hashana was inscribed for great things to happen, it's possible for a person to have reality changed to illusion. If a person is always dreaming about great things happening to him so that it seems real, so Hashem, figuratively speaking, isn't obligated to give it to him anymore.   

There was a story of a person whose business was selling eggs & chickens.  ‎Every week he would go into the Arab village, buy some chickens & eggs, go back to his town & sell them for a few dollars more then he paid. This way he would eke out a small profit to feed his family. One day, as he's walking from the village to his town with a basket full off eggs on his head & chickens on his shoulders, he begins to think & bemoan his lot as an egg peddler & how hard it is for him to eke out a meager living.

As he's thinking, he gets an idea.  Instead of selling the eggs & chickens, why not bring them home, let the chickens sit on the eggs & then he will have a thousand chicks. Of course they will all be female & have more eggs and then more chicks. His thoughts continue that, in a few months, he could have hundreds of thousands of chickens which he could then sell, ‎buy merchandise from overseas & make huge profits. Afterwards, he will be able to exchange his little hut for a huge house surrounded by gardens. Within a short time he will be appointed the leader of the town. He will lead the delegation that goes to the king on his birthday. He begins thinking about how he will bow to the king when he greets him. Because his daydream was so real to him, he actually starts bowing.

The basket of eggs on his head came crashing down; he fell on top of it killing the chickens on his shoulder & crushing all the eggs. So not only didn't he have the glory of his dreams, he also didn't have his eggs or chickens & was now penniless. Alas, his dreams had robbed him of what little he had.  
 
This, says the Ben Ish Chai, is what the Satan tries to do to us. He wants us to daydream & just think about what we‎ could do rather than actually doing anything.  By having us live in our daydreams, he, in essence, steals from us what we were meant to get for real. Instead, we were living in a dream. 

To avoid this, he translates the posuk as follows כי תבנה בית חדש , when a new thought enters your head on how to prosper either financially or spiritually, ועשית מעקה לגגך that new thought is the roof of the house, while the body of the person is the fence to give the thoughts a boundary, making sure that they don't run wild. This “fence” requires one to take what's able to be done & do it before the thoughts go wild. Then ולא תשים דמים you won't have illusions in your home & you will be able to get the actual good that's meant to come to you!