Because of the knots of Satan being untied, he becomes energetic and cheerful in the morning.

Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates from the Prophet (peace and blessings of Allah be upon him) in a marfu’ report that he (peace be upon him) said:“The Shaytan ties three knots at the back of the head of any one of you when he sleeps. On each knot he breathes the following words: ‘You have a long night ahead, so sleep.’ If he wakes up and remembers Allah, one knot is undone. If he performs ablution, two knots are undone. Then if he prays, all the knots are undone. Thus, he wakes up in the morning energetic and in a good mood; otherwise, he wakes up in a bad mood and lazy.”These are the words of the narration of Janab al-Dawraqi.