why???

i really dont understand....
why people can change after years and years although we have know he or she for a long time especially those who are our family....
why someone can speak something that hurt others so much??
have he or she think about other's feeling when heard this words??
when everybody sure that its was his or her fault,but he/she really dont realise that its really his/her fault...
why!!!
i really angry and disappointed....
but what can i do??
i just can keep it in my heart because i dont want others to know about this.....
he/she hurts everyone who heard his/her words....
how can he/she said like this!!
its really hurt....the hurt is direct go thoroughly to the heart...
i'm really crying for that for about the whole night...
i just told this matter to my "kei jie" because i really want to speak it out....
its very terrible to keep it in my heart....
i really wishing n hope that the same thing would not happens again....
i dont want to see the person that i care and love crying ownself in her room.....
and i just cant do anything.....i dont know how to facing this situation....
i'm just 17....why???