Remus is used to death.

That is not entirely accurate--Remus is used to loss, killing, other people dying. To living on: the great irony of his life. Or perhaps it is that werewolves have half the life-span of a Muggle, and yet he has outlived all the wizards he calls home.

Or it is just him.

Monthly he wants to refuse the Wolfsbane, lose his mind for a few precious hours; monthly he thinks of the people who live in this house, where Sirius slowly died; monthly he gags, swallows, manages to stay sane.

Remus is used to death.