There are things that we don't want to happen but have to accept, things we don't want to know but have to learn, and people we can't live without but have to let go.
You may not have reached a place of acceptance about your loss yet. There are people in your life who may assume you have come to terms with what has happened, but that may not be the case. Do not waste a moment feeling badly if you still wake up in a state of disbelief. Losing someone who was a part of your life is not something that you can ever take lightly. Even if the passing was expected, the feeling of loss is often much more powerful than you thought it would be. Continue to be patient with yourself. The acceptance may take a long time, but it will eventually come. With that acceptance will be a sense of peace that will help with your healing process.