Writing nonfiction, in particular the personal essay, has one major drawback. The writer can't make it up as she does when writing fiction. In a novel, the characters can say and do totally outlandish things. The writer literally 'creates' the dialogue and events that occur. Not so in the personal essay. Even though it can be termed 'creative nonfiction,' the writer must adhere to the truth. She has to stay with the facts, what actually happened.
The personal essay is normally written in first person because the writer is relating something that happned to her. I recently read a personal essay done in third person, and for me, it lost something, but that is my opinion. When the writer uses the 'I' form, she's stating that what happened is the truth, that it actually did happen to her.Most readers accept that fact when they read a personal essay, so they don't question what they're being told.
Sounds simple, doesn't it? Just tell the story as it occurred. But writers are creative people, and they might want to ehance or embellish the facts a bit to make the story more interesting. To do so is not acceptabe. It comes down to telling an untruth, even though the writer didn't mean to lie at all. Their aim was to make the story more interesting.
If the story needs expanding beyond the actual true happenings, it's time to step back and take a good look at the subject. Ask yourself if what you're writing about is strong enough to be a personal essay. Does the event and your opinion deserve publication?
Keep to the facts, and you'll never have to defend yourself later.