First of all, the exercise of Chapter 5 is the first one where we are starting with a visualisation exercise. After the first 4 weeks/parts were spent obtaining physical and mental control, plus physical and mental relaxation, here we are starting to work on our visualisation powers, or our imagination.
As regards the content of this part, "awareness" or "attention" is everything. Why? Because it means looking closer, paying "attention" to the details, thinking and analysing what is best. Haanel mentions that when we are building a home, we are selecting only the best material available, and suggests that for the construction of our mental, physical and moral home, we should do exactly the same.
Become more attentive. Don't judge when you see something or something happens or someone says something to you, but observe. Distance yourself from the story, watch it dispassionately from a distance, because this way, being less emotionally attached to it, you will observe more details, giving you more clarity. This clarity is needed to then identify patterns, get certainty, become centered, become calm and rested, and based on that make intelligent decisions.
To sum it up: if you don't pay attention, you will not become successful, because all success stems from someone looking in places and thinking up things where no one has looked before or thought before. The rare stuff is the valuable stuff - compare a glass of beer with a glass of 25yr old whiskey and you know what I mean.