How are we going to get kids in the writing frame of mind if they don't have good self esteem? When is the last time you felt like doing something artistic or creative because you were upset with yourself, or the world around you? Can't be done.
You have to feel good about the day, your accomplishments, family matters, the works. Then and only then can you reach deep inside to muster up something that you can show the world. Creativity is helped along by feeling good about yourself.
Self esteem is often about the influences around the individual. And when children are involved, it's a parent's responsibility to teach some friend proofing. You are their primary source of approval and discipline, so it stands to reason that their view of themselves will have a lot to do with you.
They may also be lacking confidence, and a clear sense of who they are today. It happens to everyone from time to time, but some can shake it off better than others.
The solid foundation that is laid as a child, and the maintenance of that foundation are crucial. Without some healthy, periodic re-enforcement... over time, repeated bad feelings may lead to some forms of depression.
So, as a general rule, you shouldn't attempt to force your child to be bright, cheery and creative when they are not ready. Be a good role model, support your child and listen to them. Have a meaningless talk or discussion with them to stay connected. And, most importantly, learn about your responsibilities regarding your kid's health.