how to cope with loss?

my grandfather died 7 months ago, and he was a Korea veteran. my grandma has stayed at my house since then, in the room right across the hall from mine... but recently she got a condo and she moved out of my house today. she gave me his Korea veterans' hat, which was his pride and joy. having this piece of his life is bringing back a huge wave of depression and anger. i found out about his death via text message from someone who wasn't even related to him, while i was at school. i am a freshman in high school and found out in 8th grade. how do i cope with this? i have started breaking down and crying every time i see the hat, which is every time i walk into my bedroom, but, i just can't take it down or put it away. what do i do?