A sense of humor... is needed armor. Joy in one's heart and some laughter on one's lips is a sign that the person down deep has a pretty good grasp of life.
Hugh Sidey

The one exclusive sign of thorough knowledge is the power of teaching.
Aristotle

As my father used to tell me, the only true sign of success in life is being able to do for a living that which makes you happy.
Al Yankovic

If you want to be a great leader, remember to treat all people with respect at all times. For one, because you never know when you'll need their help. And two, because it's a sign you respect people, which all great leaders do.
Simon Sinek

Nothing in man is more serious than his sense of humor; it is the sign that he wants all the truth.
Mark Van Doren

An interest in ideas is a sign of human life. People are fascinated by what the future is going to be - and the future is going to be an accumulation of ideas.
Thomas Heatherwick