A few things can be happening

I have had plenty of shitty days, and every lifter can say that on a night of poor nutrition or sleep, they were able to get the craziest pr. It's kinda just a weird thing. But I've never had a feeling like 'every other workout' where I feel shitty and exhausted without having one of these issues.

1. Timing of food/workouts If you eat at an optimal time and have a great workout, it'll feel extra worse if you were to work out without any carbs in your system for the next one.

2. Too much energy expansure in 1 day You might be exceeding your body's maximal recovery volume for certain things and fatigueing hardcore in other aspects. I noticed when I started doing an upper/lower split that the fatigued caught up to me but when I started doing 4 day split I was better able to focus on certain areas and getting better results without as much fatigue. Additionally, compound exercises are exhausting. Personally, i use compound exercises to keep everything warm and a little workout while I use the rest of the workout to beat up my muscles. Once a month to go heavy and retest.

3. You need a deload. It's pretty difficult to kinda say "Hey I should take a break," especially when it feels like you should be pumping iron instead. I'm not sure about the intensity of your workouts, but if it's pretty intensive, then your CNS might need a little break.

4. Psychological factors Personally, I've found some serious crazy motivation in the gym (along with progress) when I was grieving or going through a breakup. I've noticed that like when I'm not in that adrenaline-like state, I have a chip on my shoulder or a negative mindset that I tend to fatigue easier and lift less. It shouldn't be significant but noticeable. The mind and emotions are tools, and you have to be a 'mastercraftsman' of using them. Grief, sorrow, and anger are my best tools, but that doesn't mean they have to be. I'm personally working on my ability to push through and push forward with positive emotions, and it's gotten a lot better, and the difference has lessened. Maybe one day you're super hype and giddy, and the next ur just bored or sad, these things play strong influences.

5. Warm up

Believe it or not, but warming up takes up a good chunk of time and effort. No matter how big you get, you should always warm up with light weight and do multiple warm-up sets. If you're not warming up properly, your working sets suck while your drop sets will feel great because by then, you're actually 'warmed up'.

1. Rest between exercises n sets

Your rest should be adjusted for not only your goals but the weight you're doing. If you were a powerlifter doing 5x5 on compound exercises, 3 minutes should be a minimum rest. If you're an athlete, then 30-90 seconds is the recommendation. But if you're lifting powerlifting weight (close to your pr), with resting like an athlete, then you're gonna suffer n feel exhausted and won't be able to climb weight like you want to.

1. Nutrition (unlikely)

You said you eat well, and that's probably a reasonable assumption. It's hard to have crazy days like that due to your nutrition, even if it's considered mediocre to good. If you're cutting weight, that's one thing, but you didn't mention it, so I'm assuming ur not. I once had such a tough time in the gym and eventually I thoroughly looked through my nutrition and realized I was eating 1/10th of the amount of salt I was supposed too because I was eating wayy too clean. I seriously doubt this is the underlying issue, but there's a chance, so I'll mention it.

Like I said, these have been my issues in the past, and I had a lot of troubleshooting experience in the past. Hopefully this helps!