Truth and diary-keeping

I have kept diaries on and off throughout the years. There is a trend, in that they tend to more factual in 1970, becoming more emotionally focused in 1974 and beyond, presumably as I discovered the full gamut of adult emotions.
When re-visiting my diaries now, various thoughts about the truth keep popping into my head. The most important one is at the end of this piece of writing, so skip down now, if you wish!
Firstly, we will never know whether I wrote the truth in my diaries. (But what is truth?) Presumably I was writing some version of the truth. This will have been impacted on by (a) whether I thought anyone else might read the diary and (b) whether I could perceive and face the truth myself. I have to ask myself, what did I omit or embellish at the time?
Secondly, when I transcribe my teenage diaries, now, for public consumption, I don't always present exactly what I wrote at the age of 14. I might leave out things that might hurt others, or that might reveal something that is too personal about self and family. This week I even left out a corny joke that made me feel uncomfortable (am I trying to protect my 14 year old self, who existed 40 years ago, or the adult me, who still contains her?).
Thirdly, my diary keeping was imperfect, and so recently there have been questions about parts of my narrative that I cannot now answer, because my memory isn't good enough. So some truths are lost.
Fourthly, and MOST IMPORTANTLY, I have re-read some diary entries recently which have given me a sudden realisation of a truth that I didn't know at the time I made the entry. For example, transcribing my teenage diaries for this blog, (and in the course of doing so, imagining what a modern, adult readership will make of them), I saw my parents' relationship differently. Even more recently, I was re-reading a series of diary entries that I made in March 1988, when I was going through a messy relationship break-up. I can't write the detail here, but I suddenly saw something that I didn't see then! Not just an emotional insight - I saw a truth about facts, that had stayed hidden to me all this time - I have new knowledge! I think this emerged through re-reading the whole, swiftly, after a gap of many years. It was like a detective novel - this happened, and this happened, so of course, we must conclude that that must have happened! It has come as a bit of a shock, but one which the passage of time has made safe, and I can even laugh about it. If I meet any of you in person, I may even tell you the secret!

Any great insights about truth in here? Maybe not. It all links in with qualitative data analysis of course. And the nature of truth. Now I need a cup of coffee.