For one period of my life, I enjoyed woodworking and built quite a few pieces of furniture. I would work out the design, purchase the materials, cut and shape them, and finally assemble all the parts together. Then I would paint or stain the piece. Since I made the whole thing, I knew all about each finished piece. Once I cut the material too short and the width of the intended storage cabinet had to be scaled back. Another time a cutting mistake caused the grains of two parts of a tabletop not to match up. In other words, the defects, covered-up or not of each piece, I knew.
Since God made each one of us, likewise he knows everything about us. In fact, since his mind is infinitely superior to ours, he knows us through and through, and sees all out defects, our sins. So, living as if God exists is not good enough ~ we must live, being aware that he knows everything about us.