OT but physics is a funny beast like that. It's absolutely possible to study hard for months, understand everything, do past papers and still fail dismally. Every question is almost unique, and you'll spend pages and pages deriving an equation applicable to a specific situation from scratch.
It's the study of nature, think of all the possible occurrences that can happen in the universe, you can't possibly prepare for it all. The best you can do is try do find commonalities and and get to the point where you can figure out the rest on the fly.
It's not like say, second year calculus where you obviously build upon past experience and get to the point where you can do the questions in your sleep.