I think that part where you say 'a few hours later' is your problem. I am only at PPL level but as i would believe it...you should sleep then try it again when you arent so uptight about the last time you failed. I know this....when you sleep you store the information learnt during the day, therefore its better to study at certains times in order to remember more!
Im not sure if you have the time but if you do then let its best to rest for at least one night then revise it again and im sure you will do much better.
Only my opinion but thats all i can give you.
Cheers
Dave