Nice words to live by come in many forms, including single words such as "positive" or "patience" and memorable quotes such as the anonymously phrased "we are judged by what we finish, not by what we start." Words capturing different sentiments appeal as nice to different people.
Most words and phrases chosen to frame a way someone lives focus on inspirational, spiritual or motivational aspects of life. An example of this is the Walt Disney quote, "If you can dream it, you can do it."
Other words to live by seek to concisely capture finding meaning in the everyday moments that people sometimes find weary. For example, Aristotle once wrote, "We are repeatedly what we do. Excellence, then, is not an act, but a habit."