Answer:
Pouring a glass of anything to drink or milk into a cereal bowl, you must use the angle of flow from the container as it arcs down into the glass or bowl. Lets say you are pouring milk into a cup. the cup is x units high and goes up perpendicular to the counter you are using. You must raise the milk up more than those units high. How much more? Depends on the angle you try to pour the milk out of plus the amount of curve in the arc of the milk coming out. Too high and the arc will go beyond the cup entirely. Too low and you don't even make it to the rim of the cup. On the rim of the cup, and the cup might fall over or the milk might splash against the opposite side and splash out creating a mess. Not that great of an example, but it's something you may do every day. Your mind constantly calculates basic things so that it can survive.