How do I get my girlfriend back?

help me a was in a relationship with my best friend
she we are not together any more don't know whats the reason
she just stops talking to me whenever I ask her the reason
we were very serious and we decided to get marry in future
many big changes ocurred in my life just for her
ans she also adjusted herself to be in relationship
her parents said whoever the boy she gets marry should be having a god job
now she tells her dad would kill her if she suggests my name to him for marriage in future
I became workaholic just for getting good grades I m enough good to get good grades but according to her I should get more
I changed my everything just to be woth her and she also
but she is not now with me
I want to back with her
she just gets tempered if I ask her the reason for the break up
I m very high tempered person as far as I know myself
if I m very angry I even don't think of anyone just do the things what I want but not the wrong things
I controlled my angriness for her
she doesn't like me to be tempered
I need help
please help meee
I m unable to concentrate on my studies just because of her and
when she was with I was doing all things to keep her happy na d also was able to concentrate on my studies
none of her and my friends know about our realationship
I told her everything that I have adjusted and will also adjust according to u ( her )
so now what would the answer ???

tell her that you need to know the reason she left you...and its selfish of her to not let you move on by not telling you.if the reason is she dosent like you than you must accept this ...you will find someone else...but you must controll your temper,my fiance has the same problem.and stop changing everything you are for someone
be urself...although high grades are important but you must get them for you and your future not anyone else
hope this helps
-v-