Mark Twain once wrote, "The two most important days in your life are the day you were born and the day when you find out why."
The first of these days is difficult to write about and perhaps a bit boring compared to the second.
Write a story about the moment a person discovers his or her purpose or true identity or meaning. There is nothing better.
Here is Twain's full letter and, being the contrarian he was, he signs it "Falsely yours," rather than "Yours truly."
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My dear,
The two most important days in your life are the day you were born and the day when you find out why.
The day you plant your feet into this world, and the day you find out why you should use them to walk, and maybe – walk far. These are two of the four milestones of your life, they are the most important of the four because the others can’t happen without them, and every day in between is just about learning and building yourself up to these.
The other two milestones are farther down; the third milestone is the day you accomplish your why, and the fourth when you help someone else find theirs.
Falsely yours,
Samuel Langhorne Clemens