Things to worry about:Worry about courageWorry about CleanlinessWorry about efficiencyWorry about horsemanshipWorry about…Things not to worry about:Don’t worry about popular opinionDon’t worry about dollsDon’t worry about the pastDon’t worry about the futureDon’t worry about growing upDon’t worry about anybody getting ahead of youDon’t worry about triumphDon’t worry about failure unless it comes through your own faultDon’t worry about mosquitoesDon’t worry about fliesDon’t worry about insects in generalDon’t worry about parentsDon’t worry about boysDon’t worry about disappointmentsDon’t worry about pleasuresDon’t worry about satisfactionsThings to think about:What am I really aiming at?How good am I really in comparison to my contemporaries in regard to:(a) Scholarship(b) Do I really understand about people and am I able to get along with them?(c) Am I trying to make my body a useful instrument or am I neglecting it?  
In a 1933 letter to his 11-year-old daughter Scottie, F. Scott Fitzgerald produced this poignant and wise list of things to worry, not worry, and think about – the best father’s advice since John Steinbeck’s letter to his son on falling in love and this beautiful letter to 16-year-old Jackson Pollock by his dad.
From F. Scott Fitzgerald: A Life in Letters.