One of the best ways to have a healthy sleeping is to plan your exposure to light. When you’re exposed to light your brain stops producing melatonin (the sleep hormone). Which makes you not sleepy anymore.
Darkness tells your brain to feel more melatonin, which makes you feel tired and fall asleep. At night, prepare yourself a schedule to turn off most of the lights and get into bed.
This will help you get/fix your sleep schedule for the new year.