Even if you don't believe in an afterlife, you can do the exercise of writing down the things that you feel you did to wrong the people that you're talking about, how it's making you feel, how you imagine it made them feel, and what you'd like to do about it if they are still alive.

Sometimes if people are feeling guilt about something they did to someone who is no longer living, they choose another way to make amends, like doing something to further a cause that the person believed in or doing something for their surviving relatives.

I'm including a link to an article about self-forgiveness and making amends. A formal process of evaluation and making amends if possible can help your grief to take form instead of being so overwhelming and amorphous.