Sleeping - How much is enough

[sweetwater]

...and when I tried to force myself to sleep longer, I also woke up headachy and grumpy - the medical folk said it was due to poor quality sleep, leading to low levels of oxygen, (proven by the oxygen sensor I wore during the sleep study). I'm not trying to sell CPAPs or medical services, it's just the enthusiasm of the newly-converted. I resisted for years, thinking poor quality and limited sleep was just my 'normal'.