Grief is individual. Everyone experiences the sorrow over the loss of a loved one in their own way and at their own pace. That said, there is enough common ground for scientists, behaviorists and psychologists to describe steps or stages of grief. These scales for grief are useful. They can be helpful to see your feelings mirrored in the process and it is good to see that progress is to be expected.
In his book, Grief Counseling and Grief Therapy, William Worden takes a little different approach. He describes four tasks the mourner must accomplish.