Why must the narrator write her journal in secret

The narrator has been prescribed a rest cure and is prohibited from exciting herself as she is diagnosed with a 'nervous condition' which nowadays would be identified as post natal depression.

Gilman based the story on her own experiences and the mental frustration which tortured her as a writer and intellectual condemned to inaction. In the story, the narrator hides her journal as she knows it is against her husband and doctor's wishes. Her husband sees writing as the expression frivolous womanly emotion,

'There comes John, and I must put this away,--he hates to have me write a word.'