Dont give up. Just keep trying. Maybe an other way of studying can help you. Try to find some ways you can combine to have a bigger chance to succeed. When i needed to do exams, i recorded the most important things on tape and played it over and over again when i was sleeping. Test showed that our mind is processing things differently while we sleep. It worked for me and it is not a big effort. Maybe you can try this to and see if it helps ;)