Yes, this is a real issue, not just an excuse.
You could try the suggestions above - but you might have to experiment. If I get into a hyper-focused mode, it will take a lot more than a watch going off to get my attention. I've sat still so long I had to drag myself up by my arms, because I didn't even notice my legs were cramping.
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AQ Test = 44 Aspie Quiz = 169 Aspie 33 NT EQ / SQ-R = Extreme Systematising
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Not all those who wander are lost.
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In the country of the blind, the one eyed man - would be diagnosed with a psychological disorder