The Sleeping Buddha represents equanimity or Upekkha, which is the final virtue of the Four Brahmaviharas. With Upekkha, we learn to accept gain and loss, praise and blame and success and failure with detachment. Detachment is a neutral state of the mind, which is not holding onto anything, big or small, significant or trivial.
"Before the Buddha's death, he became severely sick. He walked northwest with his disciples and had the food offered by a blacksmith. His illness was getting worse. In the end, he came to a river and took a bath. Then he made a rope bed among eight sal trees, with each direction has two. He lied on his side, right hand supporting his head, the other resting on his body. All later reclining Buddhas (called Buddha's Nirvana) are in the same posture. The Buddha's disciples kept watch on him after they were told the Buddha was going to nirvana. At night, a scholar of Brahman went to see the Buddha, but was stopped by Ananda, a disciple of the Buddha. Hearing this, the Buddha called the scholar to his bed and worded for him. Thus the scholar became the Buddha's last disciple. The final exhortation of theBuddha to his disciples was that they should not be sorry for losing their tutor. Their should take the Buddhism Doctrine as their guide, eager for progress, no indulgence. After his death, the Buddha's remains were cremated.