Harry decided that the only way he can win this war with his sanity intact is to train his own way without interference. But then he discovers an ability that he needs help with and only one person can provide that-Tonks. They bring the fight to the DEs in their own way so that the war will finally end.
“Clear your mind!” wasn’t actually the best advice. Harry is fed up and takes things into his own hands and discovers a way to end the war on his own terms. No one was expecting this of the Gryffindor Golden Boy.