“Sleep that knits up the ravell’d sleeve of care,
The death of each day’s life, sore labour’s bath,
Balm of hurt minds, great nature’s second course,
Chief nourisher in life’s feast.”

‒William Shakespeare, Macbeth

Why We Need Sleep

Shakespeare may be complicated, but the universal need for sleep is not. The “Chief nourisher” is, indeed, a major function of sleep. It scavenges toxins produced during the wakeful hours which are literally “the death of each day’s life.” It results in “hurt minds” or damage that may be irreparable. Sleep scavenges and disposes of the poisons that allow the system to be revitalized with a “second course” or another day.