dont be angry, as a matter of fact
be happy.
value and treasure ur mistakes. keep a list of ALL ur mathematical mistakes uve ever made. write next 2 each mistake what the mistake was and how to do it correctly.
treasure ur past papers that u havent gone so well in. the only way to stop commiting these dumbass errors is to learn the 'error', not the 'question' itself.
i had the same problem in a test, i knew the question. i knew how 2 do it, blah blah.
stupid mistake and i got screwed over.
i kept a list, i worked on my errors. and a 2 months later the next exam comes along.
AND I FUCKING RAPED IT!!!!!
its all good.