The Computation

For the first twenty years since yesterday
 I scarce believed thou couldst be gone away;
 For forty more I fed on favors past,
  And forty on hopes that thou wouldst they might last.
 Tears drowned one hundred, and sighs blew out two,
  A thousand, I did neither think nor do,
  Or not divide, all being one thought of you,
  Or in a thousand more forgot that too.
 Yet call not this long life, but think that I
  Am, by being dead, immortal. Can ghosts die?