He is a pathological narcissist, and pathological narcissists need constant attention to survive.
His campaign has never stopped because he is in front of an audience and has to absorb his admiration (however bad they may be) and worship (how out of place). He will not let that sit behind closed doors in the White House, which is why he is constantly holding rallies and happily preaching the same philanthropic hatred of the same happy hateful crowd over the last two and a half years.
Beware: If he loses the next election – and he will indeed lose – he will first accuse Dems of manipulating the election. Then he can go to Fox News and preach to the rafter about how he got a rough deal. Being a narcissist, he can not understand that The Great Donald Trump loses in any other way than if someone has cheated. And with the tongue of Fox News sitting firmly on his butt, he knows at least that he'll be on TV every day.