How do you manage to work for hours on end without a break?

Why is this your goal? It's actually pretty hard on your body over time. I recommend taking a brief stretch-get-up-and-walk break at least once an hour or so.

I always (arrogantly) disregarded this advice as a young'n because I felt fine at the time. Twenty years later I now have a seriously arthritic neck / back. Very painful everyday.

Caveat emptor.

I find I have the opposite problem. I zone out coding and 3 hours go by and I haven’t taken a break, walked around, or even had a drink of water. I think remaining focused is a mixture of a couple things: low/no BS work culture, low meetings/distractions, and ownership over code. I think having ownership leads to wanting to make improvements more often, which makes me more motivated to work more. Really, I should be more strict about taking breaks. It’s better for your health in the long term.

... Ask amazon warehouse and Ford production line workers. You manage by forming a union, and refusing to work for hours on end without a break.

I try to avoid days where I need to work for hours on end without a break.

But sometimes it's inevitable and I can't get into the zone.

I then take Ritalin.

Stuff needs to get done . . .