Any parent who has had more than one child knows that children have very different personalities. Although most children do the same things - like playing, eating, sleeping and getting up in the morning - how they behave while doing these things can differ greatly. In other words, children have characteristic ways of dealing with the world, based on their temperaments.
Children are born with their temperament - it's a genetic tendency. Temperament affects how active or attentive a child is, how anxious, shy or adaptable to new situations, how irritable or intensely emotional, and how sensitive to sight, sound and texture a child is.
A child's personality is a result of the interactions between that basic temperament and her many experiences with you and other caregivers during these early years.
For parents of children with more difficult temperaments, some situations and days can be challenging beyond belief. However, it's important to remember that many difficult children become some of the most exciting, contributing adults.
It's how you adapt to your children, and how you help them adapt to the various environments that they encounter - such as home and childcare and school - that can really affect how they'll do over time. This means accepting your children as they are whenever you can, seeing their behaviour in a positive way and helping to ease them into various childcare and school environments. If you can do that, it can sometimes help them "smooth out" some of the more difficult aspects of their temperament and to develop a more well-rounded personality.