If you live in your head, reality always comes as a surprise. And you never have to change your mind.
Donald Trump is a realist and a pragmatist. He has to be, because he wouldn't last in business if he was mentally fixated on only one way to get things done. So he's tried and failed, changed his mind many times, kept what works and dumped what doesn't work.
This is pretty much what realists have to do. The United States has just (barely) survived eight years of Obama, who is a fixated ideologue. Obama never listens to other people because he is cognitively stuck.
When the Arab Spring failed, he didn't turn to Egypt's President Abdel Fattah el-Sisi, who managed to save his country from the Muslim Brotherhood. Obama just kept supporting the MB's in Egypt, because they are just as mentally fixated as he is.........