Yes, I failed two mocks, having breezed through every exam before that, I wasn't making full use of the time.
I spent far longer on the actual exam, taking my tutors advice (that I ignored on the mocks!) and went back through all of my answers the following morning before submitting. I found a few mistakes where I missed some key words, only small mistakes but they would've cost a lot of points due to knock-on effects. Unsurprisingly I went from scoring around 80% in the mocks to scoring 98% in the exam.
Are you self-studying or using a training provider? If using a provider, definitely follow the tutors advice, mine gave me some very handy tips which are unfortunately mostly out of date now.
It is definitely a tricky exam as seemingly small errors can have such a big effect on the overall score, the key for me was reading everything fully and carefully, then double checking all of your answers when you're feeling fresh later/next day.