One thing is that there is no formula. I have felt that lost sensation before, what to do, how to act. Give yourself plenty of freedom and grace, and also those that are grieving along with you. Everyone has highs and lows in the grieving process, many times we say things we wouldn't normally say, or do things we wouldn't normally do. Allow yourself to express what you need to express, and allow others to as well. I can't really make anything easier for that, just know many have gone through what you are going through, and take solace in that.
I am sorry you lost a friend, it is a painful experience. I lost a 20 year old friend to cancer, a cousin to a car crash, and my Grandpa all in the past few years. It still hurts, I still think of them. It will happen again, it will happen to me. We all take precautions, we know what we are up against, I'd much rather die in the water with my PFD on than at 2 am on a lonely road. I will continue to paddle, and I will do my best to be safe, but the river may take me.
Sorry again, friend.
Wishing I was on the river instead of surfing the web...