"자신에 대해 자신감을 가지는게 좋아! 넌 멋진(or 좋은)사람이야" Actually, "멋진사람" means a handsome person and "좋은사람" means a good person, but when we use "좋은" or "멋진" to describe a person, they describe the one's personalities or human being. Thus, "멋진사람" sounds like "A person who has handsome personalities" for Koreans. Well, the translation is kind of weird but I believe you probably got the point. Sometimes, we use "멋진사람" for actually handsome people, but it is kind of too formal to use. Like in English, people would use a cool guy or awesome people rather than a neat guy or wonderful people. You can say "훌륭한 사람", it literally has the same meaning as a great person but it sounds like a google translation or a quote from textbooks.

자신감을 가져야해요. 당신은 훌륭한 사람이에요.