Sorry for your loss. I lost a close co-worker once and it was extremely painful. Do not hesitate to cry if you want to. Laugh at some of your good moments, joke

Sorry for your loss. I lost a close co-worker once and it was extremely painful. Do not hesitate to cry if you want to. Laugh at some of your good moments, jokes. Say something to him out loud if you want to "Hey Gregg, how would you solve this problem?". I hope you continue with your project, I am sure Gregg will support you along the way.