Life is very hard to let go of and death difficult to accept for those left behind. No matter how many years pass many continue to grieve and often out of guilt cannot let go. If only they had done more, been there for the person more often etc that person would have lived longer. No matter what you tell yourself we each have a set life here. We have chosen our birth and death dates long before we come here. No matter what you did or didn't do you still couldn't have changed anything.
A priest once said,"Don't grieve for too long otherwise that person gets trapped here."  Excessive grief traps the dead and the living cannot move on.
Give thanks for their life and realise how much it has added to the richness of your tapestry but never cling to those memories. Move forward with happy memories in your heart.