Folk Metaphor: If Dog Rabbit
Erics interpretation of this saying is, if the dog hadnt stopped to take a shit then he would have caught the rabbit. This term is mostly used when playing card games. Erics grandfather passed this saying down to him, and Eric most often uses it with other family members when they are playing card games, like poker. This term is used anytime you use the word if and/or engaging in wishful thinking without taking any action.
The word if is emphasized in this saying, symbolizing that one needs to take actions in order to produce results. You cannot expect to achieve goals if you are always making excuses for yourself. I could imagine that this phrase may have been commonly used amongst hunters with hounds and may have been later passed down to sons and daughters. I could also see this phrase used in different contexts besides card games. When one is aspiring to try out for an audition but is hesitant to do so and they say if only I could try out for the ballet, an encouraging person could push them to audition by telling them If dog rabbit.