I've heard it said that "be yourself" is bad advice because some people are jerks and should not be themselves. However, I disagree. Being a jerk is not part of a person's identity. A jerk who stops being a jerk is becoming their true self.
"The quick brown fox jumps over the lazy dog" is an English-language pangram—a sentence that contains all of the letters of the English alphabet. Owing to its brevity and coherence, it has become widely known.