I do wonder whether given enough effort you could train an OCR program to be pretty good at recognising one person's handwriting. Like if you meticulously corrected the output and added those corrections to your training set, would it eventually be perfect (or close enough anyway) or would it hit some sort of fundamental limit?

Clearly some peoples' handwriting sure. Good handwriting recognizers take advantage of stroke recognition, which you can't do by OCRing after the fact.

In addition my handwriting has become terrible. If I check my notes soon after writing them (within the same day) I can often tell by making out a few words and remembering what was being discussed when I was marking that part of the page :-(. A couple of days later I can barely understand them and longer than that I might as well forget it.

I could probably get by making random marks on the paper!

It's so sad, because when I was a scientist and had to maintain a lab notebook other people could easily read my notes (and they had to be clear for IP reasons). Or maybe I should look at it the other way: it's not sad, because it doesn't matter as much any more.