My advice is - first, get a driving instructor, and a good one - possibly one recommended by your friends in your area. The reason is simple - whilst it is true that the instructor will be a big expense, they know what is required on the exam, they know the process that gets you from being a newbie to being capable, they know the mistakes people make and they will correct you. They also know the standard exam routes that your driving center uses and drive you around these without end so that these routes become familiar to you.
My driving instructor was always telling me - mirrors - check them - gas, break, clutch etc and we always drove in the area around the test center and always corrected bad habits I had from watching my mum drive such as not holding the wheel in 10-2 and crossing my arms when turning it etc. These are things that examiners look at and things that your parents won't spot and don't know how to deal with. My driving test was almost exactly like one of my lessons and I was calm and simply followed instructions. I knew the area, I knew where I was going and I was told the commands in question hundreds of times before. Fiscally speaking, you'd have probably spent the same money with an instructor as you did on tests.
Second, it is possible that the place where you're doing your test is difficult to pass in. I live in a moderately hilly area of London but my driving instructor teaches his students in a posh flat area instead, where most drivers are calm and polite and there are almost no problems with hills.