One of the things that continues to amaze me in my personal fitness journey is how often I forget that not being sore doesn't mean I'm recovered. I fall for this all the time. Example: I hit 140kg on my squat this week and felt sore in the hips for a day but no big deal. Two days later I think I'm good to go and I start squatting and all of a sudden 100kg feels heavy. For some reason, I still have this impression in my mind that if I did 140kg two days ago, I should be good to go for nearly that again two days later, but it never works out that way.
This is one of the reasons wave loading exists. You wave the weight up and the reps down then in subsequent workouts you lower the weight but raise the reps. It's smart training for one thing -- you hit many different areas and attributes like this. You can cover power, muscle building, and endurance all in one week. But it also gives you time to recover from the more intense trainings. Funny how I just fell into it naturally because I couldn't lift heavy all the time.
So yesterday I found myself doing high reps with a paltry 70kg in the squat yesterday simply because my body was telling me I could move but I needed a break from the heavy iron.
But let me tell you this -- it really messes with your head to drop from 140kg back to 70kg again. You MUST remain calm and not freak out that you're doing something wrong. This is the body's natural reaction when you're training hard.
Enjoy the journey.