If your child is sharing their concerns with you - don't try to jump in and solve their problem by giving advice. Instead, try offering your child a few minutes of your focused time to just listen. As a parent this can be tough. None of us want to see our kids hurting. But by giving your child some time to formulate their thoughts, as they discuss what it is that is actually bothering them, you are providing a supportive framework for decision making. Don't go over the top when validating or offering support. A few calm, well meaning words will do the trick.
Or try this: Show your support by posting a small note on your child's bathroom mirror. Make sure that the note is placed at their eye level so that they are sure to see it. Write something simple like, "Believe in yourself, because I believe in you!" or "You are ready!" or even "So proud of you!" or "Today is your day!"
Mean what you say and say what you mean. If you say that you are there to support your child, hold back any criticism or disappointment if they don't do as well as you or they had hoped.
After the challenge, add a "high five" or "congrats" note to the mirror. Even if your child was unsuccessful, lost or struggled to meet their goal, recognize what they did do and encourage them to continue.
That night, add a Hershey's kiss and a note on their pillow telling them that you love them. Silly, but oh so meaningful to a young child!