I also think so much has changed in the last 15 years. When I feel overwhelmed at the loss and waste (still!) I send love to his spirit and ask for forgiveness for not having seen it coming. And try to do something special for someone else.
!ENGAGE 25
You really cannot blame yourself for not seeing the signs, I know from personal experience how easy it is to hide those feelings especially if it's someone close to the depressed person as you don't want to upset or hurt them. I used to have the same feelings about my brother for many many years till my healing started.
Take care of yourself @artemislives!