Why don't you go fetch it?
Dogs are sort of the optimists of the pet world. They're just here to have a good time. So what if they didn't catch that tennis ball? There are a ton of other tennis balls out there! Eventually something we'll come their way again.
Check out this beautiful Tastefully Offensive video supercut of dogs utterly failing at fetching things, and the dog's not really caring one bit, because ... CHECK OUT THAT OTHER THING OVER THERE!