How do i give up my arrogance?

i'm extremely confused.please help me.people say you have to be arrogant,but then it is not nice to be so.i hadn't called my teacher whom i had promised and then she called the 2nd time and it didn't even come to my mind that i should apologize.my mom said i was becoming self centred.there are many instances when i have received the same comment.but then my sister and many others say that you need some level of ego and arrogance to survive in this world.i don't know where to draw the line.whatever i do i over do it.and i am not finding any support from my family which consists of a pesky grandma,and alcoholic dad and mom(she undergoes mood swings as it is menopause time for her),a sister who is hardly at home(i meet her only on weekends,when she'll be quite busy).i don't know how to develop my attitude,i'm running 16,i read a lot of chicken soup books and try to improve myself,but it will have a negative effect.please give me some self development tips!help me grow into a better person