Samurai were encouraged to meditate on their deaths and to think, "If today were my last day, would it have been a worthy one to be my last?" When I've taken this practice I've found myself working on more important things, spending time with people I care about more, and generally being happier. Highly recommended, quick further reading:

The Budoshoshinshu at Google Books:

http://books.google.com/books?id=gzFsCPYJhqEC&printsec=f...