What is the meaning of "'This is no flattery: these are counsellors / That feelingly persuade me what I am.'/ Sweet are the uses of adversity ..."?
The Duke was surrounded by flatterers when he was in power. Now he calls "the seasons' difference, as the icy fang / And churlish chiding of the winter's wind" his counsellors because they are at least honest with him and tell him the truth about his human condition. He has found that his adversity has had some positive benefits, especially in teaching him to love nature, to value peace, and to be accompanied only by honest and loyal friends (his "co-mates and brothers in exile"). The main thing he has learned from his experience in the forest is that the simple life is the best kind of life, even if it involves some hardships. It is the kind of life that Robin Hood enjoyed. The Duke concludes his monologue by saying, "I would not change it." He would not go back to the mendacity and artificiality of court life. People often find that adversity (bad luck) can really be good fortune because it forces them to learn new things and to make beneficial changes. Adversity can bring out adaptability and strength of character in all of us.