In "My Life Closed Twice Before Its Close", how does Dickinson describe the two events that befell her?

In the first line of the poem, Dickinson says, "My life closed twice before its close -"  These were 2 events that were so dramatic and overwhelming, that she is comparing them to death, to her life actually shutting down, and closing.  These events could have been the death of a loved one, or another extreme form of disappointment or trial. 

She goes on to say that these events were "So huge, so hopeless to conceive".  She is anxious of another event that would be so hugely difficult, and concludes that "Parting is all we know of heaven./And all we need of hell."  These events were so awful, the "partings" that she had to take (of a loved one, of hope, of her previous perceptions, whatever it might have been) that she calls them "hell".  She also calls them "heaven" because in death, that is the closest mankind comes to heaven.  As usual, Dickinson's words are few but packed with meaning.