Self-harming is often a way for a troubled character to temporarily relieve pressure and cope with some form of pain. It can have many causes, such as work or family stress, being bullied, alcohol or drug abuse, and certain mental health conditions. Self-harming can be a progressive behavior, and it's often a symptom of a more serious issue, so this is a particularly dangerous secret to keep.

Personal Health Issues (primary); Dark or Disturbing; Regrets, Guilt, or Shame

HAVING A MENTAL HEALTH CONDITION, STRUGGLING WITH A CHILDHOOD TRAUMA

ABANDONMENT, BEING A BURDEN TO OTHERS, BEING JUDGED, BEING LABELED, BEING PITIED, BEING SEPARATED FROM LOVED ONES, BEING WATCHED, CONDITIONAL LOVE, CRITICISM, HUMILIATION, ISOLATION, LETTING OTHERS DOWN, LOSING AUTONOMY, NOT BEING IN CONTROL, REJECTION

Not addressing the root cause of the self-harm, which is perpetuating the self-harm and likely additional problems
Feeling like no one will understand them
The character's mental health deteriorating to the point of suicidal ideation or attempts
Feeling shame or self-loathing about their behavior
Unsuccessful attempts to stop the self-harm resulting in feelings of incapability and despair that keep the character from trying to make other positive changes
Being afraid to attend events where the wounds would be seen

Wearing clothing and makeup to hide their wounds
Lying about how they're feeling; always acting cheerful or upbeat
Carefully disposing of evidence of the self-harm so no one will find it
Cutting or hurting parts of the body that are easily hidden
Never going to locations that require a bathing suit (a pool, the beach, etc.)
Having explanations for how they hurt themselves

Reluctance to continue with therapy sessions (or increasing the frequency of sessions)