You should really take regular breaks in your day. Really? When do I actually have time? I am still working on what I was supposed to complete yesterday. This was totally me when I was working as a field engineer for many years.
I remember it very clearly. I was hunched over my laptop in a little control room on a water plant startup site sitting for hours at a time with snacks and a gallon of water(hahah yes this was me with my big old jug of water). I wonder why I was a stiff all the time, not even taking a break to eat lunch most days.
Now times have changed and I do TRY my best to take more breaks so I hope you can too.