4 sets of 12, let's say.
I pick a weight and try to get all 4 sets of 12 and don't (at least not the first time).
I keep using this weight for all sets until I get 12 reps on all sets. Clean reps.
Then I up the weight (maybe by 5 pounds if it is a Dumbbell) and start over, getting as close to 12 across all the sets as I can.
20x12, x12, x12, x10
20x12, x12, x12, x12
25x12, x10, x8, x6
25x12, x12, x8, x6
25x12, x12, x12, x6
Complication makes it easy to explain failure.