You should pick up things that you drop.
John is five and at the dinner table with his parents where they are all enjoying a meal together.
John wants to finish the meal, so he can go play.
John accidentally drops some food because he is eating so quickly but notices his mistake and immediately cleans up the mess.
John in his haste drops some food on the floor but continues to eat his meal.
John's parents politely suggest he slow down and then dismiss him from the table, so he can go play.
John's parents make him clean up the mess and don't allow him to play as punishment for ignoring the mess.