I have my camera ride shotgun when I travel, that way I can get a good photo, if one rears it's head. I like to be ready just in case. I also have my phone camera if needed.
Nothing wrong with off days. Some of the funniest pictures come from off days. You captured a very fast dog, and it makes me think that he's actually trying to get a cat. Nice shot. Love how it's not totally still, but has plenty of blur.