I've never been one to keep a travel journal, and my field notes tend to be relatively dry - they're owned by my employer and subject to be rifled through during discovery for potential litigation, so I don't have a lot of local color in my field notes. You can get a pretty good sense for when I'm having a bad day, though, because you'll find a lot of pointed "spoke to person X, who told me this, and then person Y told me something completely different, and then because of conflicting directives, this other thing got missed".
Back when I was in my field study course in college, I was pretty careful to follow the requirements for logbooks - numbering pages, having thorough observations and maps, and recording things like temperature and time. I didn't have a lot of side observations. One thing I did was collect flowers and press them in the pages of my logbook.
This was back in the day of non-digital photography (remember then?) and I'd been conserving my film so that I wouldn't miss anything spectacular while I was out in the field. Then my camera died right at the end of the first roll of exotic field photographs, and I lost the entire roll and the use of my camera for the rest of the trip. When I returned home and got to a camera shop, my camera was diagnosed with a terminal case of "sand in everything", so my only mementos of that time are those pressed flowers I kept.
In lieu of photos of me doing fieldwork (since I didn't have any), here's a photo of what killed my camera (from NPS photo):
It was a lovely way to go, I'll admit!