Whether is a diary, journal, memoir, or poetry, if you let it slip that it's private, people will want to read it. Here are some tips on how to keep it secret.
1: Use a decoy journal. Make a fake journal and hide it in a place that the snooper will look. Make the entries believable or address the snooper correctly. "I sometimes worry that people are reading my diary. I think you know why SNOOP.".
2: Hide your journal in a hard to find spot. Snoopers look in usual places; at the bottom of your desk drawer, your bookbag. Try inside of a folded sweater, taped to the lid of a shoebox, behind books on a shelf.