As a general rule, it is normally considered unacceptable to peek into the diaries of friends, even those you hold close to your heart. The first point to make for anyone who suspects that they may figure in the narrative is that there is only the dimmest chance of reading anything complimentary about yourself.
Private diaries are for candour in more instances than otherwise, which is one good reason they are looked upon as sacrosanct territory. Another reason against is that experience shows that diary entries are not always the most accurate sources of information about the writer's life story. Many a diarist escapes from dull reality into the realm of fancy and wishful thinking, as many Love Stories readers would be able to attest to.
Notwithstanding the likelihood that the entries may be factually misleading, I suggest there are exceptional cases in which breaching the unwritten rule of confidentiality can be justified. Others may disagree with this twist of ethics. But my feeling is that when someone in your care or to whom you owe support is distressed and you are in the dark as to the cause of their pain, you may be forgiven for seeking any help you might find in the pages of Dear Diary.
Mostly though, illicit diary peekers have no such moral imperatives and are simply itching with curiosity about another's private thoughts. Few are totally immune to the impulse, if the truth were told. Which brings me to the question of an excuse, should someone be caught in the act. My counsel is to apologise immediately and to dissemble, if only to support your blushes: you had no idea it was private and were just flicking through to check a date.
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