Vastu means the dwelling in which one lives. Shastra is the science in which explains how the energies in this dwelling work. Your house is a blue print of your subconscious mind. Based on your horoscope and destiny you decorate our dwelling. Thus when there are hurdles or challenging situations in our life caused by certain planetary positions in transit, the same changes are seen in our dwelling. Thus rectifying the changes in the dwelling helps to overcome the situation.