The trouble being, to the pet parent grieving (who likely HAS heard this...or the corollary, "When are you getting a new one?" like they're bags of chips you pick up when you run out), they won't get any further than the title before tuning you out.

Although, thinking about it... if the second was a thought balloon, with "It's only my heart" that would get the message across, that you not only understand the loss, but the stupid "helpful" comments from people who DON'T understand.