Thank you for sharing your grief here on PC. I'm so sorry for your loss. You wrote that, although you did the best you could, you can see how you could have done things differently. I suspect this is the way we all feel at times such as these. Hindsight, as we are always told, is 20 / 20. Here are links to 3 articles, from Psych Central's archives, on the subject of grief & loss that hopefully may be of some help. The first article, by DocJohn, provides links to quite a number of additional articles on the subject:

Coping with Grief | Psych Central

Grieving as a Path to Connection and Meaning: A New Perspective | Healing Together for Couples

Thoughts on Memories, Grief and Loss

My best wishes to you.