Like others have posted, there are times that I wish I had kept a journal, but for the most part, I didn't.
I bought my first shotgun, a Miroku 12 ga O/U just before I left Vietnam in 1970. When I got home I started reloading for it and for a while I kept track of every box of shells that I loaded for it: the case, primer, wad, size and amount of shot, and what I shot with it, including including the number of trap targets that I broke with that box. That record keeping didn't last long and now 50+ years and 250,000 - 300,000 reloads later the only records that I have are some Trap and Skeet trophies and some 100 straight pins and patches.
That book also has records of all of the boxes of rifle and pistol shells that I loaded and shot. The last date of those records was 1975.
As for hunting records, I shot my first mule deer and first elk back in the mid '60s when I was in college and all I have now are the memories of those two hunts and I think that the elk antlers are still hanging in the rafters of my garage, along with the antlers of most of my other elk. The only written record of any of those hunts is a couple of pages in the book that I recorded my early reloading data. There is a line on each of those pages for each elk that I have shot, listing the year, number of points on each antler or if it was a cow, where I shot it, and the rifle and sometimes bullet that I used.
After moving to Montana in 1975 and up into the '90s I had some fantastic hunting, killing a deer, elk, and pronghorn antelope just about every year along with 3 Unlimited bighorn rams, 2 Shiras bull moose, a Mountain goat, and an Alaskan Caribou. All of those hunts were DIY and most of them were solo. I didn't keep a journal of any of those hunts but I did have my 2 best bull elk, the rams, moose, goat, and caribou mounted.
In 2001, after a nasty two year divorce which was just a property settlement for a 10 year marriage where she wanted half of the value of all of my taxidermy, including mounts that I had before we even met, I started a computer record of all of my taxidermy including the year that I shot the animal, the year that it was mounted, the taxidermist, the cost of the mount, and the rifle and bullet that I used.
So back to the topic of this thread, I have been big game hunting since 1965. Most of my hunts were DIY in my home states of Colorado and Montana. Although I got some great animals on those hunts, I didn't write any journals of them. I went on my first guided hunt in 1999 then 16 more guided hunts here in North America and around the world.
It wasn't until after my second African hunt that a year or so later I couldn't remember the names of PH's or their staff that I hunted with or many of the other details of the hunts. So in 2017 for my third African hunt I decided to keep a journal of it. Every night before going to bed I wrote down the details of that day. That journal was 41 pages long!
I ended up writing much shorter journals of my last three African hunts, but nothing on any of my other international hunts or of my hunts here at home. All that I have now for most of my hunts is fading memories and a home full of mounts. Some would say that I've gone overboard with my taxidermy (80 mounts), but other than some of my pronghorn antelope mounts, I can look at each mount and remember every detail of that hunt.