If you could score 78, reaching 80+ is no big deal! All you need is crispy tips that actually work. You need to find gray areas in your enabling skills so that you can precisely focus on the items you need to work on. For instance, a student had come to us with a problem in speaking as rest of the sections were fine with her. we discovered that the breathing sound of her was one of the factors. We worked together, and well, she could overcome it.
So, check your enabling skills and confirm where you need to practice more. Taking more tests will boost confidence in you. Consider computer as your friend, and speak freely. Include some complex words, and read the pasages carefully - this all can help you get 80+.