You raise a subject I need to address more. Setting goals and not meeting them is not a disaster. It's part of learning where boundaries are.
Not meeting a goal and failure are very very different things. It's how you look at the meaning of the words. For example, you could say that a person fails many times before she succeeds.
I don't think failure is the right word there.
They did a study many years ago about success and failure, involving ice skating. About 40 people who had never skated in their lives gathered on one side of a pond. The goal was to get to the other side of the pond while skating.
People slipped, slided and fell many times. Some gave up after a few falls. Others continued to fall but stayed the course and got across the pond.
Results: the people who fell the most were successful.
I love this study. Children need to lean how to fall and get up. They need to learn what it feels like to overextend such things as their time, strength, ability, developmental stage, finances and learn.
They need to learn that achieving a small part of a grandiose goal can be terrific. It can be the beginning of learning what it takes to do more. It can be the beginning of learning that they don't want to pursue that goal.
Being a child in a safe, wise and loving environment gives the child the room and space to try things, explore, miss a goal, not do well, try again or change her mind and redirect herself.
In my opinion we support our children's strength of mind, heart and character when we teach them that others cannot define our children's failure or success. That is for the individual to decide. (And she needs to be free of an eating disorder to make her wise and realistic decisions.)