Why does his happen? Test are supposed to prove that this information has successfully entered my head? Why does it feel like a purge? I spill my guts out on the paper and its like i have nothing left.
True, however self tought is not worth as much on your resume as formal education.I want to say you crammed. Studying... what, 30 minutes after a lecture, using deeper questions to encourage application of what you've learned, digging into the whys of which information is useful, etc. Helps bring information into long term memory with better clarity. Loads more study techniques and whatnot.
Let's say that isn't the case: I usually forget things after a test because the subject material itself was rather bland to me. So the purpose of retention is now served and no longer important after a test. "I forget to recall that which has no need to be remembered," kind of thing.
Education sucks. At least, structured, institutionalized education does. Self-education for the win!