For MG (middle grades) and YA (young adult):
I wrote in a different post about six-word biographies for your character.
This is a development of that, with the suggestion of writing multiple bios based on where the character is in the story. They should change and what they are thinking about and focused on should change as well.
Write a six-word biography for them before the beginning of the story, when life is going on as usual.
Then compose one just after the call to action or inciting incident. How has your character’s life changed?
Then create one for when they go through the rising action, attempting and failing to solve their problem(s). How are they feeling? What are they concentrating on?
Write another for them at the climax of the story.
These should be very different and may help you get a handle on the character’s feelings.