Ouch! That looks ... gnarly.
I am not a rookie, but I try to remind myself that I am not a "black belt", either.
With regards to always wearing the seat belt:
My operator manuals all instruct that:
If your ROPS is up, then your seatbelt should be on.
If your ROPS is down, then your seatbelt should be off.
-Jim
Here is my rookie mistake from January 2014. My new tractor was delivered the same month. I was putting the brush hog away, lowered it onto the 4 wheel dolly and began pushing on the upper link with one hand above and one below. As you know the upper link moves up and down and will fully collapse if you push on it from above. Here is the outcome.
View attachment 445450
Read your Operator Manuals... front to back. Then re-read them with a highlighter pen in hand.
Invest in a very good set of ear protectors and wear them. Insist/advise that others wear a set if they're in close proximity.
Ear plugs and safety glasses any time I'm brush hogging for sure. Seat belt too. Good leather gloves in my pocket or tool box for when needed.
I've made it very clear to my kids to stay away when the brush hog is running, in my 30 years of operating a tractor/brush hog, I've seen plenty of projectiles ejected. Even had to ask my neighbor to not stand nearby when watching me a few weeks ago.
Never too old to learn new things, including safety habits.