Your calendar defines who you are. What you value should be reflected in how you spend your time. If you say you want to get in shape or start a business, but spend each day on the couch, you are lying to yourself. The calendar, on the other hand, never lies.

More:

You Are Your Calendar (YouTube video) by Tom Peters 

Death Clock (extension for Google Chrome) – Every time you open a new tab in Google Chrome, this extension reminds you how much time you have left (based on your age and the current life expectancy stats)

100 Blocks a Day + Your Life in Weeks (articles) by Tim Urban