Comment by kentich

I'd suggest trying to work in intervals. I use Black Screen (https://blackscreen1.com/) to black out my screen for 3 - 5 minutes every X number of minutes. I start from 30 minutes and gradully reduce the interval as long as I'm getting more tired - even down to ridicules 5 - 10 minutes. The interval should be long enough to have an undivided attention span. If you get distracted then set up shorter interval. This approach helps me a lot lot.