It's very important to let children establish their own goals - to play the game for themselves. Take care not to impose your own standards and goals on them. Don't put too heavy a burden on your child to win games. Children play for the fun of playing. Positive reinforcement is the best way to help your child achieve their goals and their natural fear of failure.
Nobody likes to make mistakes.
If your child does make one, remember it's all part of learning, so encourage your child's efforts and point out the good things your child accomplished. They volunteer their time to help make your child's youth soccer experience a positive one. They need your support too. That means refraining from coaching or refereeing from the sidelines.