COULD has no problems sleeping at night. COULDN'T is afraid of the dark and has problems falling asleep at night. COULD shares that there is nothing to be frightened about the dark and the two soon fall asleep. The Series Big Life Lessons for Little Kids CAN, CAN'T, COULD, COULDN'T, DID, DIDN'T, WAS, WASN'T, WILL and WON'T -- known collectively as the CAN DO s -- are all friends and they each have something to teach your child. From sharing and perseverance to doing homework and being a good sport, the CAN DOs help you as a parent lay the foundations for a well-rounded, confident and outgoing child.