Rooney stated last month that he would not sign a new contract with United, after failing to receive assurances over squad-strengthening.
But two days later he agreed a five-year stay, with Ferguson glad the England striker realised he had been hasty in going public over his concerns, which were met by an angry response from many supporters.
Ferguson believes the advice Rooney received was not in the 25-year-old's best interests.
"You don't necessarily have to heed advice after listening to it," Ferguson said. "Some young people take bad advice. He has an agent who is not the most popular man in the world and he obviously sold it to Wayne to ask away. The boy rushed in.
"But the minute he heard the response of the public and our supporters, he changed his mind, he knew he'd made a mistake."