According to lifehacker.com, Jerry Seinfeld has a productivity secret that helped him as a young comic in need of great jokes. His advice followed like this:
1) buy a big wall calendar and a magic marker
2) for each day that you accomplish your task (his was writing jokes), put an X over the day
3) after a few days you create a chain of X’s, and you will be inspired to keep the chain alive
4) DON”T BREAK THE CHAIN!
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http://lifehacker.com/software/motivation/jerry-seinfelds-productivity-secret-281626.php