Think of the last set that felt genuinely hard. Three quick questions — answer honestly, based on that set.
This checks one set. It won't tell you your training is wrong — only whether that particular set showed potential to meet the standard.
The standard here simply means the standard of execution required to get the best possible results from your training.
Right when you stopped, could you have done another rep with the exact same form?
Did you lose tension anywhere during the set — at the top, the bottom, or between reps?
How did the set actually end?