My anecdata is different: sleep is mostly accurate, if sometimes a bit fuzzy, and occasionally misses the mark. Regarding grogginess or lack thereof, what I no

My anecdata is different: sleep is mostly accurate, if sometimes a bit fuzzy, and occasionally misses the mark. Regarding grogginess or lack thereof, what I noticed is that sometimes I feel that way even though the watch says I had good rest, but it's only so at the beginning of the day; afterwards I'm okay. Conversely I may have had a bad night and still feel okay, but what I noticed is that if I don't pay attention to the watch I'm actually plowing through and don't notice I'm wearing myself out, which I then have to repay the following days. Also the watch gives a) objective measurements (whereas my feeling is subjective) and b) measures only a bunch of things but not everything (e.g I noticed eating pasta or something weighting on my mind and morale can both make me experience brain fog that the watch does not account for)