Kubler-Ross wrote about the five stages of grief:
These stages and others are written about in greater detail in the book Rays of Hope in Times of Loss. They are useful from the standpoint of knowing there is something predictable about the unpredicatable aspects of grief! But everyone is unique and these should be thought of as flowing, sometimes back and forth. They are not a progression ensuring that once you have gone through one stage, you won't have to return to it again. Sometimes the shock we feel about someone's death turns into shock at the many changes our life must take in order to move forward in our loved one's absence. Or we may feel shocked at how someone else is dealing with their grief in a completely different way than our own. Bargaining is when we try to negotiate an "I'll do this if you do that" arrangement in our own promises to ourselves, God, or sometimes a pact we even try to make with our departed loved one. There are many examples of this that can sometimes keep one from moving forward into acceptance. The primary importance of having some familiarity with the stages and what is "normal" about grief, is that you begin to understand that such suffering is universal and not crazy. Then you can feel comforted by knowing you are not alone.