There is great value in brevity. A good quote is a short, meaningful, authoritative statement with emotional appeal.
Short: Short is memorable, long is complicated.
Meaningful: There is a huge difference between information and intelligence. Meaningful intelligence offers valuable personal insights that increase our power to act.
Authoritative: A quote should be trusted to accurately repeat the words of the author. A credible quote should be substantiated by a reference to the source.
Emotional Appeal: Our emotions tells us what we value. The things we value are the things that motivate us to act.