i m so sad :(

i m so sad..i lost my 20% in my exam..
its not because i dunno hw to answer..its not because i don't do revision..
yes,i did revision, i know how to answer...
but..i lost the mark just because of my careless, over-confidence and also my laziness.
i tot i m so pro and so geng and tot i cn score it ..
so ..i never read for the instruction..get the exam question and answer..
feel so proud and happy cz finish it early.
after discuss with my course mate, i JUST realize i answer wrongly it..
ARGH! why i so stupid and so lazy and so confident of it!!!
i m so sad..so pls leave me alone..i need sometime to cool down myself :'(