Why my mood always change???

All marks been given to us. At least I happy with my result. Another thing is, my bro also get a nice result. But... bro's mother say "this broken result you also can get 3rd place at your class?!"
When I hear from my bro, I really feel sad! Cause nearly all the subject I been teached my bro before exam....and he also got improve. But his mother say not enough!!! I really no mood at that moment...At that time, I just wanna shout out!!!! But no place let me shout!!! Today, I call some friends go out to eat for celebriting our exam results. At the begining, all say "OK", at last? All say "CANNONT COME".... another 'heart attack' for me....include my bro.....I don't know want to blame him or what?? And I just didn't have the courage to blame him... or maybe I too sayang him....and i really hope the friendship between 2 of us will become more closer!!!!
sad...........