I've probably lost about 15 or 20 blitz games in a day in the past; I still have ups and downs in rating (just dropped about 50 points just this week and trying to slowly climb back now), but since about a year or so, I implement a kind of stop-loss type system. If I am not feeling my A-game, then I take a break and if I lose a select amount of rating in one day/sitting, then I stop for the day.
Chess is highly mental and concentration-based. For this, many breaks are required to play at your best. Of course, if you play shorter time controls (and hence more games in the same amount of time) then your rating will suffer from greater variance in ups and downs: that is just the math of the rating system. Bullet players might play 50 games in one day - their variance is unreal appearing to me! As someone who plays rapid and blitz more often currently, I have trouble losing 20 or 30 points in a day lol
Yesterday I lost 10 out of 11 5|5 Blitz games I played. To be fair I was playing a little distracted but still.