Ah. Never read Watership Down. I remember several people on GAFF talking about how depressing it was. May have to take a look at it, though.
You have my smpathies. I've owned God knows how many cats in my lifetime, and it never stops hurting when you lose one. It sounds like yours led a good, long life, and that everyone had did all they could. But it still always hurts, because they become a member of the family, just like your parents and your siblings. It does matter how old you are; there's no shame in mourning the death of someone you loved, be they human or animal.