My son went through a phase at 20 months where he simply refused to sleep. Not overtired, not sick, just decided sleep was optional. I tried everything. White noise. Earlier bedtime. Later bedtime. Sitting with him. Not sitting with him. Eventually I found the combination that worked and it was embarrassingly simple. The most common reasons toddlers stop sleeping well: overtiredness which causes a cortisol spike making it harder to fall asleep, nap schedule mismatch, bedroom environment issues, developmental leaps causing brain activity, and separation anxiety. Start with the environment: room dark enough that you cannot see your hand in front of your face, white noise at a consistent level, temperature between 16 and 20 degrees. Check the nap schedule: too much daytime sleep pushes bedtime later, too little causes overtiredness. Most toddlers between 18 months and 3 years need one nap of 1 to 2 hours. A consistent bedtime routine signals the brain that sleep is coming. Bath, pajamas, teeth, books, song, bed. Same order every single night. The routine itself is the cue. If your toddler is waking in the night and calling for you, the question is whether this is a habit or a need. Hunger, illness, teething, and developmental leaps cause genuine waking. Habitual waking where they simply want your presence can be gradually addressed by reducing your response over time. The key is consistency: whatever approach you choose, do the same thing every single time for at least two weeks before deciding it is not working.