Montessori theory talks a lot about sensitive periods in childhood development and how the child is guided by inner forces that shape their developmental needs. Children pass through sensitive periods for language, movement, order, writing, reading, etc.
It is during these sensitive periods that there is a great need for total focus, sensorial exploration, and a need for repeating activities in order to master skills. Sometimes these sensitive periods are characterized by overpowering (sometimes obsessive) and intense activity.
Interrupting a child while they are in the middle of an intense sensitive period can result in a powerful emotional response (i.e. tantrum). Break a routine that a child is attempting to understand and master (i.e. getting dressed, bath time, bedtime) and some children will literally fall apart as they are most likely in a sensitive period and their intense "work" is being interrupted.
"A child learns to adjust himself and make acquisitions in his sensitive periods. These are like a beam that lights interiorly or a battery that furnishes energy. It is this sensibility which enables a child to come in contact with the external world in a particularly intense manner. At such a time everything is easy; all is life and enthusiasm. Every effort marks an increase in power. Only when the goal has been obtained does fatigue and the weight of indifference come on. When one of these psychic passions is exhausted another area is enkindled. Childhood thus passes from conquest to conquest in a constant rhythm that constitutes its joy and happiness."
The Secret of Childhood
Children can profit from various stimuli that are made available to them during a sensitive period. This is one of the reasons why Montessori materials are clearly set on low shelves and made available to the children. It allows them to choose the work that will help them 'construct themselves' - master a skill and aid in their development and adaptation.
Parents and teachers can capitalize on these sensitive periods by ensuring adequate time and materials are available, and by respecting the individual interests and passions of each child. It is through observation that the needs of the child are revealed.
As always, follow the child. And tuck some extra patience away for the days they want to repeat the same activity over, and over, and over again.