Its so hard, I lost my dad two years ago and I still miss him so much. I would suggest that you cannot actually do anything, just let yourself grieve, its a long process but every day it sort of gets easier. Dont fight the grief, just accept its going to be painful, like nothing you have ever felt before. I just sat and thought about the good things we had together, looked at photos, I still do. Dont be hard on yourself accept the help of other and tell them how you feel. Time is the best healer of all and dont be ashamed to say you cannot do the normal things in life for a while. I am so sorry for our loss.