That's some good advice. Thanks, Grandpa Jefferson

"Nothing gives one person so much advantage over another as to remain always cool and unruffled under all circumstances."

Thomas Jefferson, 3rd President, 1801-1809

Extract from letter of Thomas Jefferson to Francis Eppes, May 21, 1816 

"honesty, disinterestedness, and good nature are indispensable to procure the esteem and confidence of those with whom we live, and on whose esteem our happiness depends. never suffer a thought to be harbored in your mind which you would not avow openly. when tempted to do any thing in secret, ask yourself if you would do it in public. if you would not, be sure it is wrong.
... at all times, practice yourself in good humor. this, of all human qualities, is the most amiable and endearing to society. whenever you feel a warmth of temper rising, check it at once, and suppress it, recollecting it will make you unhappy within yourself, and disliked by others. nothing gives one person so great advantage over another, as to remain always cool and unruffled under all circumstances. think of these things, practice them & you will be rewarded by the love & confidence of the world." http://www.monticello.org/site/research-and-collections

Francis Eppes was the grandson of Thomas Jefferson. At the time this letter was written, Eppes would have been 15 years old and apparently was receiving some grandfatherly advice upon embarking on his education and career.

Eppes went on to become, among other things, mayor of Tallahassee, Florida and in 1857 helped fund and found the State Seminary West of the Suwanee River which came to be known as as Florida State University.