On August 8th of 1933, author F. Scott Fitzgerald wrote a letter of advice to his 11-year-old daughter, “Scottie,” who was away at camp. Some of his timeless advice included:

"Things to worry about:

Worry about courage
Worry about Cleanliness
Worry about efficiency
Worry about horsemanship
Worry about…

Things not to worry about:

Don’t worry about popular opinion
Don’t worry about dolls
Don’t worry about the past
Don’t worry about the future
Don’t worry about growing up
Don’t worry about anybody getting ahead of you
Don’t worry about triumph
Don’t worry about failure unless it comes through your own fault
Don’t worry about mosquitoes
Don’t worry about flies
Don’t worry about insects in general
Don’t worry about parents
Don’t worry about boys
Don’t worry about disappointments
Don’t worry about pleasures
Don’t worry about satisfactions

Things 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?”

(Source: F. Scott Fitzgerald: A Life in Letters ; via Letters of Note)