When a baby has repeated problems falling asleep, Mom and Dad may need to show some tough love. Lingering with cranky babies too long or bringing them into the parents' bedroom can make them likelier to become poor sleepers, according to psychologist Jodi Mindell, who gathered data on nearly 30,000 kids up to 3 years old in 17 countries. "If you're rocked to sleep, nursed to sleep, fed to sleep at bedtime, you're going to need that every time you wake up," she notes. Her advice: have children fall asleep 3 ft. away. "If they're slightly separated, they sleep much better," she says.