I personally don’t do reviews if I’m too tired, because I’m more likely to get them wrong and it will affect my motivation in a negative way if I get something wrong that I know the answer to.
so I just push through the brain fog to clear them, even though I end up getting a lot of them wrong because of it.
When I’m tired I go full potato-brain and I mess up even the most basic of answers. I would rather delay my review until I’ve had some rest than risk setting back a ton of the Kanji / Vocab.
You could also make the arguement if you can’t answer them when you’re tired you aren’t fluent
enough and you need to practice more, but personally I don’t think about it that way!
If you have too many reviews stacking up at once (like 200-300) you need to space them out more, so do 100 per day for example. If you do 200-300 in one sitting they’ll pop back up in 200-300 chunks anyways.
But when I look at how my reviews will stack up if I don’t clear them ASAP makes me panic
I think there is a userscipt to hide the review number so you can do it at your own pace without seeing it be at 300 and panicking.
Found it:
Just remember to thank @Kumirei if you use it 
.
You can also use this for the home page:
Is there a better way to manage reviews than this?
The only way I’m aware of is to space out your reviews into manageable chunks say 100 or less per day, and make sure you do your reviews daily - try to find time before you get too tired, even if it’s on the bus or during a lunch break. This will help with the “stacking-up”, and it’s super important for your progress.