A teaching of Jesus' during The Sermon on the Mount. Jesus tells people to shine in their example to others; practise their religion well and others will follow them.
"Be the best that you can be" is to me a great lesson. Be the best for yourself, and others will follow your example.
Again, this may be my Christian bias showing here, but it seems that this is a "default" non-religious teaching; simply a piece of good advice.