How do you use journals and why do you think them useful?
Do you think they are a place for only random thoughts, fun stuff and things that do not tie in with the storyline, or a place to enhance the storyline from the personal perspective of said character, to build on it, to bridge gaps and to tie loose ends?
I think they can be used creatively for lots of things. I have bridged gaps, tied loose ends, showing things which were partially written in the storyline, and partially implied only, deepened stories by showing a character's (flawed, but meaningful) perspective, foreshadowed some things by setting the ground in the information comprised in the journal, which would become important/ more interesting later on, tying with events which haven't happened yet.
In one case, the journals were a sideplot of the story - if the main story was action-focused, the love story was reflected by journals only (with intentions to further become half journals, half letters, but those were to be reflected also in the journal thread). His point of view vs hers. And it worked perfectly.
Looking forward to hearing your creative experience with journals, diaries, letters!