did poorly on all my finals :((

idk where i went wrong. im usually an 80% or higher student. my best grade for my finals have been a 77% this semester, with my lowest at just 59% and my most recent at 65%. 

i study, i try my best, usually this doesnt happen to me. i dont even blank on the questions! how am i so fundamentally mistaken in all my classes??? how do i do so well on the assignments and then do terribly on the finals?? 

this doesnt make sense to me at all. and this has never happened to me before.

i feel so stupid and confused.