Peeking at his girlfriend's text messages and diaries.

Everyone has his own right to privacy. You shouldn't read his diary. There are some things you haven't thought about yourself. The most important thing for two people to be together is communication. Everyone has a past. Since I chose to be with her, why bother with the past? Open your heart and trust her. If you have any dissatisfaction, you'd better clarify it face to face.