Private is not the same as secret danger.
UYB can make honest writing easier, but it cannot replace a trusted adult, emergency help, therapy, or safety planning when something is unsafe.
Both people should carry the work.
When adults write too, the journal feels less like a test. It becomes a shared pause where everyone has to name one honest thing.
Do not punish the reveal.
If a younger person gets punished for being honest, the next answer will be smaller or less true. Read first. Ask what they needed you to understand.