A short, pithy, commonly known expression which generally offers advice or wisdom.
Part list of quotations, part collection of wisdom, part collection of advice, this list a from Lessons Learned in Life is inspiring and contains many well known sayings which are well worth re-reading. (They are well known sayings for a reason)
56. Admit it when you’re wrong.
81. You are what you do. Not what you say.
97. Smile at strangers.
Full list here.