It means that you have no control over your mind. It does what it wants. Similar to how we are given a name that we had no say in choosing, this person is simply accepting that they will have certain thoughts because it’s not by choice.
I would recommend using Brutus. Through he betrays Julius, he is a man of honor and would be a very easy answer to this question. I haven’t read this play in a few years so I can’t quite but I hope that helps.