Think about how much information needs to come together to drink a glass of juice. See the cup on the table. Move the hand to grasp it. Grasp it hard enough to pick it up, but not too hard to tip it. Lift it at the right speed. Tip it to drink. Feel the heaviness to know how full it is. If any information is missing, juice is going to wind up on the floor. If that's a common occurrence at your house, consider whether motor planning could be a problem for your child.