Write All The Time.

"To Quentin Roosevelt
December 24, 1917
Dearest Quentin, 
Mother, the adamantine, has stopped writing to you because you have not written to her -- or to any of us -- for a long time.That will make no permanent difference to you; but I write about something that may make a permanent difference. 
Flora spoke to Ethel yesterday of the fact that you only wrote rarely to her. She made no complaint whatever. But she knows that some of her friends receive three or four letters a week from their loves or husbands (Archie writes Gracie rather more often than this -- exceedingly interesting letters). Now of course you may not keep Flora anyhow. But if you wish to lose her, continue to be an infrequent correspondent. If however you wish to keep her write her letters interesting letters, and love letters -- at least three times a week.
Write no matter how tired you are, no matter how inconvenient it is; write if you're smashed up in the hospital; write when you are doing your most dangerous stunts; write when your work is most irksome and disheartening; write all the time! 
Write enough letters to allow for half being lost. 
A hardened and wary old father."

Theodore Roosevelt was the 26th U.S. president and a father of six children. The letter above was taken from Dorie McCullough Lawson's Posterity: Letters of Great Americans to Their Children.