Child development is a continuous process from conception through adolescence. The age at which children develop certain specific skills in motor activity, language, and in social and emotional growth, varies from one child to another. Each child grows uniquely. Children's growth and development will be continuous, though not constant. There will be spurts in growth.
Children often go through a change of behaviour or mood just before they learn something new.
This is typical. For example, sometimes a baby may experience many fussy nights just before learning to sit and crawl. Children usually accumulate many aspects of a skill and then practice the skills that they have learned without further learning. The child repeatedly goes over previously learned activities. The plateau period is necessary for the child to perfect the skill being learned.