The following allegory was shared by the Ben Eish Chai, Rabbi Yosef Chaim of Bagdad (died 1900).
There were once two donkeys. One was carrying a load of salt. The salt was very heavy and the donkey struggled mightily to bear his burden. The other donkey was carrying sponges. He didn’t even feel his load and walked gleefully on the trail as if there was nothing on his back, whatsoever.
Eventually they came to a stream. When the donkey, who was carrying the salt, entered the water, the salt began to melt. After a few minutes the salt totally dissolved. By the time he emerged from the stream, he was carrying empty sacks on his back. Relieved from his burden, he began to walk with happiness and ease.
Whereas, when the second donkey entered the stream, water rushed into the packs and flooded the sponges, creating a very heavy load for the donkey. Indeed, the weight was more than he could bear and the donkey’s life was endangered as he struggled to keep his head above the water.
Thus, the heavy load of salt served to benefit the first donkey because after he entered the water, his load was lifted, and he found ease and tranquility. Whereas when the second donkey entered the water the light sponge turned into an unbearable burden that nearly cost him his life.