: a moral rule or belief that helps you know what is right and wrong and that influences your actions

: a basic truth or theory : an idea that forms the basis of something

: a law or fact of nature that explains how something works or why something happens

Full Definition of PRINCIPLE

a :  a comprehensive and fundamental law, doctrine, or assumptionb (1) :  a rule or code of conduct (2) :  habitual devotion to right principles <a man of principle>c :  the laws or facts of nature underlying the working of an artificial device
Having a Purpose in life is not by itself.  You need a road map I call principles.  Those written by God.  Those guidelines and compass lead my faith and learning. My principles come from the word of God.  It is the compass to life.  So are the help of many great scholars, teachers, and “solid” preachers.  Wise men seek counsel with the wise and wise men still seek Him.  It is not always easy to follow this compass.  That is why it is called “to run with patience that is set before us.” In Hebrew 12:1-3.  It takes perseverance and endurance.
 – DW
“All you need is the plan, the road map, and the courage to press on to your destination.”
-Earl Nightingale