One way to compare your training session from today, with the workout you did last week or one you are planning for next week, is to figure how much you lifted. This can be called "volume" or "tonnage" or "work." People sometimes get worked up over jargon, so focus on the concepts, not the words.
Sets x Reps x Weight
3 sets of 8 with 375 equals 9,000 pounds lifted.
Increasing weight(from 375 to 400), while keeping sets and reps the same(3x8) would increase the total work done.
Dropping the reps down(from 8 to 5), would remove some of the work from the load.
Obviously, this doesn't tell the whole story. You can't just deadlift 6,000 pounds for 1 rep and call it a workout. But you can evaluate your workouts against eachother.
You did about 9,000 pounds worth of deadlifts last week.
This week, you add weight, but do fewer reps per set. The bar is heavier, but you don't feel as wiped out because you did less total work. Only 6,000 pounds worth.
It's possible that you feel so good, you decide to do a few back off sets. Lets say 3 sets of 10 with 275. That's theoretically doable?
Those back offs just added a lot of "work." If you add that to the heavier sets(6,000 + 7,500=13,500) you can see you did way more than you did the week before (9,000). If you felt beat up after that, and you can't recover by your next Deadlift session, you could do less in the future.