Are you feeling guilty that you were not there with your friend and are you thinking that if you were there, you could have changed the end result? If you are then you are experiencing a lot of guilt. The reason I ask is my husband is going through the same feelings. We lost his mom last week to a heart attack and he keeps thinking if he was there he could have performed CPR and brought her back. This "what if" thinking makes it very hard to heal.
It sounds as if you cared for your friend a lot and of course, this is extremely difficult for you. It does not seem like it is getting easier but believe me, one day it will. For some of us, it takes longer than others to be able to enjoy life again. The pain will always be there but it does become more bearable.
I hope you have people to talk to if you need that personal support. But keep talking about it. It helps more than you know. I hope you will find the way to healing soon. Hang in there. Let us know how you are doing