A lot of people have kept, or perhaps still are keeping, a diary. I, on the hand, have never really been the sort of person to keep a diary.
When I was young, most of my entries were just random stuff that I wrote for fun, and of course I took pleasure in illustrating them. As I grew older, the diary was more frequently used to vent about something that upset me. But it wasn't very often that I wrote in it when I was upset. Sometime around junior high, I stopped writing in the diary altogether, and it just became part of the enormous collection of journals, sketchpads, and notebooks.
Part of the reason, I think, was because I never felt much of a need to write in it, and never really got into a habit of writing in it. The other reason was because when I looked back at some of the things I had written in the past, I hated them. It seemed that whenever I tried to express my emotions when upset, what I wrote didn't sound like me at all. It sounded like some messed-up or ungrateful kid. I sometimes over-exaggerated things, or complained about stuff that really didn't matter. At one point in time, I actually went through my diary and tore out all of the pages that I didn't like, and those pages were thrown away.
Then again, maybe the problem is something different entirely. Perhaps it's just a matter of perception, and how it often changes over time. The things that seem so important at the time are later seen as trivial. In the long run, that argument you had with someone is as significant as a single speck of dust amid miles of desert sand. And of course, there's the simple fact that a person's worst critic is themself. We tend to focus too much on our past mistakes and criticize ourselves too harshly.
So I don't really keep a diary. It's not the style I prefer to express myself in, and it didn't work well for me in the past. These days, I typically express my thoughts through poetry, fiction stories, or on my blog. It tends to work better for me, and I'm usually more satisfied with the result. Everyone has ways of expressing themselves, they just have to find what works best for them.