He is a tall, dark man who walks with confidence and is sure of himself because of his success in the world of business.

sure 的意思是"确信的、有把握的"，表示对某件事或某种状态有坚定的信心。 of 在这里是介词，表示所属关系或属性，连接"sure"和"himself"。 himself 是反身代词，指代主语"he"，表示"他自己"。 sure of himself 这个短语表示"对自己有信心"，指一个人对自己的能力、判断或价值有坚定的信念。