You are committing mistakes because you do less practice. You should write at least one full length essay per week and get it checked by a good teacher. Last year, I wrote around 3-4 complete essays and I was overconfident that I will perform well in the exam with no practice at all. But, sadly, I couldn't. This happened due to lack of practice. Right now, I am busy in my masters and job so unable to give proper time to preparations. But, what I aspire to do is to work on my grammar and write one essay per week, IAT. This is what you are supposed to do. There is no rocket science in it. All you need to do is to practice and learn those rules that you have written.
Offer prayers as well. It will help you a lot. By the way, there is no rule of 'afraid', it just lies in you. Kill it
Cheers !
Stay blessed.