CHKWAN,
I am sorry to heard that you dad was passed away last sat. We all here can understand the heart broken feeling you are suffering now. As what you told, your father passed away with a calm face. I quess he is now in a peaceful & joyful place. Think about it what your father will want you to be - I quess he will like to see you have a happy face and live more better than anytime else before. Hope you can recovery from your sadness and sorrow soon!
May God bless you and your family!