LEGO Design/Strength
Sometimes you want to build something that will not fall down if it gets bumped or dropped. When you are building the walls of a house, for example, make sure you build it well. Just like in a brick house, the bricks are not stacked right on top of each other. They are staggered. This gives strength to your building, and creates a strong foundation from which to build your creative incarnation.
Strength is important when building with LEGOs. In case it gets mis-handled while being moved or built, it might break. Hours of hard work could literally crumble away. A strong creation will last its part.