Become a Lake

After growing tired of her novice's complaints, a sage sent her novice to get some salt. When the novice returned, the sage told her to mix a handful of salt in a glass of water and then drink it.
"How does it taste?" the sage asked.
"Bitter," responded the novice.
The sage instructed the novice to put another handful of salt into her pocket while they went for a walk. The novice did so. They walked in silence to a nearby lake. The sage said, "Mix your salt into the lake." The novice swirled her salt in the water.
"Now drink from the lake," said the sage.
As the water dripped from the young woman's chin, the sage asked, "How does it taste?"
"Refreshing," said the novice.
"Do you taste the salt?" asked the sage.
"No," replied the novice.
The sage and novice sat on the rocks beside the lake. The sage explained, "The pain of life is pure salt; no more, no less. The amount of pain in life remains exactly the same. The amount of bitterness tasted depends on the container into which the pain is placed. So when you are in pain, the only thing you can do is enlarge your sense of things. Stop being a glass. Become a lake."

How do you stay a glass? How do you become a lake? Which would you prefer to be? Why?