It's imperative for a child's healthy development to feel important and worthy.  Healthy self-esteem is a child's armor against the challenges of the world. Kids who feel good about themselves seem to have an easier time handling conflicts and resisting negative pressures. They tend to smile more readily and enjoy life. These kids are realistic and generally optimistic.  It's also been shown that children who feel important are well-rounded, respectful, and excel in academics, extracurricular activities and hobbies and develop healthy relationships with their peers.  

In contrast, for children who do not feel important or cherished have low self-esteem, and challenges can become sources of major anxiety and frustration. Children who think poorly of themselves have a hard time finding solving problems, and may become passive, withdrawn, or depressed. 
You are the biggest influence in your child feeling important, valued and worthy.  Remember to praise your child for a job well done, and also for putting for a valiant effort.  Praise the good traits they naturally possess, and help them find ways to learn from their mistakes and failures.  Be honest and sincere in your praise.  Help them realize that you also suffer from self doubt and can make mistakes from time to time, but that you know that you are important, valued and loved.  When you nurture your own self -esteem and importance, your child will learn to do the same, so be sure to lead by example and steer clear of self-depreciating yourself or engaging in activities that lower your self-worth or importance.  

Your child may have inaccurate or irrational beliefs about themselves, their abilities or their traits.  Accentuate the positive about your child, and encourage your child to set realistic expectations and standards for themselves.  Help them identify traits or skills they'd like to improve and help them come up with a game plan for accomplishing that goal. Encourage your child to become involved in cooperative activities that foster a sense of teamwork and accomplishment. 
Through these and other positive, affirming activities, your child is sure to develop a strong sense of self importance, value and worth which will carry into their adult years.