On my workout on fridays at the moment i'm soing 3 sets of max reps with 165lbs and a couple of weeks ago I could lift it 12 times on the first set, 10 on the second and 10 on the third. Today I did it and the first set could only lift it for 11 reps, second set for 10 reps and the last set for about 7

Is there any reason for this or have I just got weaker?
This annoyed me sooo much i felt like i was going to explode and only just managed to finish my workout as I was in such a bad mood.
Please tell me there is another explanation other than I got weaker
Is there any reason for this or have I just got weaker?
This annoyed me sooo much i felt like i was going to explode and only just managed to finish my workout as I was in such a bad mood.
Please tell me there is another explanation other than I got weaker