I have been in your situation many times, especially over exams. One day during results, I decided instead of worrying and crying for hours and hours I would remain calm and simply leave it to God and put all my belief in him that I wouldn't fail- I did not let even 1% of my mind focus on the chance of failing. And guess what- I ended up with the highest grade i've ever got- although I was certain I wouldn't do well, and I was so surprised!
I learnt to build my faith through the years, and ended up with a First Class in my undergraduate and Distinction in my Masters. Now you may be thinking- good for you, but I wanted to show how I was in exactly the same situation as you, full of fear and worry. I learnt that God can give you so much more than you ask for, all you need to do is build your faith from your heart, and you will be amazed at what happens.