A in a level maths

Hi, I'm aiming for an A grade in a level maths. I do edexcel maths. Wrote my final math mocks today and I felt prepared as I revised every topic over the easter holidays and did multiple questions on them. However, I noticed that I usually make lots of silly mistakes or write the correct thing and erase it or I have the working in my head but for some reason I don't write it down and then I end up regretting it(or it's along the right lines). I'm not sure if this is due to anxiety but this happened in my previous mocks(which I got a B in)
Does anyone have tips on how to get over this , to get the best grade possible? Thanks

It sounds like you just need to believe in yourself more. Maybe when you do practice questions when you revise, write down what you think initially and stick with it, then check the answers. That way you'll know if you were correct the first time around or not.