All children feel insecure sometimes.
Between the ages of 6 months and two and a half years, most children experience separation anxiety, or fear whenever mother is out of sight or the child is left at day care or with a sitter. This fear, as well as other insecurities throughout childhood can cause sleep difficulties and even nightmares. This is something that most children will get past if they feel loved and supported. As children get older, they still may have times when they feel insecure. For instance, some children develop school phobia or fear of being away from home.