One of the worst feelings of sickness that I ever face is being nauseous. Because for me, I usually know what's coming next. I know the Bible speak of the Great White Throne, but being bent over the great white porcelain just doesn't seem to measure up! Throwing up is disgusting. The very idea of it is nauseating. And when it does happen, I am quicker than the speed of light to make sure that it flushed, cleaned up, or whatever necessary to get that moment in time as far into the past as I possibly can.
It's bad enough the humiliation of something disgusting happening the first time in our lives, but to return to it again is even more disgusting. The term for "dog" was used as a humiliating description of reproach, also referring to the disgust of a male prostitute. this proverb equates all of that with the idea of a fool returning, repeating, or duplicating a choice of stupidity, silliness, and foolishness.
How disgusting and humiliating it is in the eyes of the Father to duplicate or return to those habits or cycles that He has sought to free us from. We need to see them as disgusting, as reproachable. We must not ever try to justify or compare our sins and struggles with something that looks "worse." In God's eyes, it's all foolishness and to return to it makes us a fool.
But be reminded of this truth: Our God is a gracious, loving, and forgiving God. He is bigger than your struggle and He will not only give you the strength you need, but if you let Him, He will be the strength you need. We don't want to return - but to advance in the direction God has called us to.