When someone I love (dog or person) is ill, it strips away most of the fluffery of daily life. Not only does it become meaningless, but I can experience difficulty recalling who I was were when I once cared about it, (and most likely, will again, although in a changed and leaner fashion.) It's possible to have moments of wonder that the world is carrying on around me, while my sense of it is shaking and rocking like a vase on a rickety end table.
Life can be good even as it's painful. I don't see it all as simply as I once did, and that complexity creates a more satisfying life, even when my heart is aching for the suffering of those I love.