Angela Lee Duckworth, in her TED Talk talks about 'Key to Success'. She left her job in Management Consulting to go teach Seventh Grade Maths class. She then went on to become a psychologist.

Her conclusion after years of observation and methodical studies conducted? She asked -  'Who is successful here and why?'. Her answer. Four letters
GRIT = "Passion and perseverance for very long term goals. Grit is having stamina. Grit is sticking with your future, day in day out, not just for a month but for years. Grit is living life like it is a marathon, not a sprint." - Angela Lee Duckworth

Online dictionaries define Grit as 'Indomitable spirit' or 'resolve to do something difficult or unpleasant'.

Her closing words - "We need to be gritty about getting our kids grittier"