Fasting

"Daniel 6:17 And a stone was brought, and laid upon the mouth of the den; and the king sealed it with his own signet, and with the signet of his lords; that the purpose might not be changed concerning Daniel.

18 Then the king went to his palace,

What is significant to me is that a heathen fasted for his friend and denied himself things that gave him pleasure. This is a king subjecting himself for a friend.
For God how much more is expected from us? Going to your father by denying yourself seems rite, what do you think? and passed the night fasting: neither were instruments of music brought before him: and his sleep went from him.
19 Then the king arose very early in the morning, and went in haste unto the den of lions."