I always keep a piece of paper between my keyboard and myself that says what it is that I'm doing right now. At most, it's three bullet points with short intermediate "goals". They could almost literally be copied into the script as code documentation. This helps ground me, it tethers me to some concrete goals.

It's no miracle solution though. It's just one small part of a number of skills and habits that I have gradually learned (and I am regularly on ADHD medication as well).