Young Writers Society

So I am writing a novel and I thought it would be interesting to include journal entries from the protagonist, in addition to the normal dialogue/prose. The only trouble I am having is keeping her voice consistent in the journal entries.

For example, in one entry she is discussing the pain of losing her father and how her family is not coping well with it. It is a very adult voice, with some pretty awesome metaphors. But then, in another entry she is writing about her first date with a guy that she feels is way out of her league. Her voice here is noticeably young and immature, focusing only on the superficial details.

I really don't know how to fix this. Any suggestions?

First of all: Are the journal entries necessary at all? They can add an interesting twist, sure, but if you don't need them and can't get them right, then maybe it's best to cut them altogether.

Secondly: If you do decide that you want to keep them, it might help to figure out what she's like in different situations. Different settings, people, and happenings can bring out different streaks of her personality. Her father dying was tragic and heartbreaking, so she was probably at a time in her life when she thought deeply about things. Her date with a boy out of her league probably made her feel happy and like a teenage girl again. There's probably some surge of power going on there, too.

So the voice, whereas it has to stay the same in terms of writing style, can be a little different depending on the mood of the entry. I'd look back and try to pick out different quirks in her voice to implement throughout the entries, so she still sounds like herself in all of her moods.