The Dip: A Little Book That Teaches You When to Quit (and When to Stick) by Seth Godin

The 80-page "The Dip" is a really short business book, with a succinct message: "Quit the wrong stuff. Stick with the right stuff. Have the guts to do one or the other." According to USA Today, "the legendary football coach Vince Lombardi was wrong when he said, "Quitters never win and winners never quit." In Godin's view, "Winners quit all the time. They just quit the right stuff at the right time."

Seth Godin gives at least one wrong example though: ".... if you took organic chemistry, a killer class, in college, you've experienced the dip. Academia doesn't want too many unmotivated people to attempt medical school, so they set up a screen, he explains."

Actually, you need organic chemistry in order to understand biochemistry, physiology and pharmacology, which are studied later, not because somebody set up an artificial screen.

References:
Review: Better know how to handle 'The Dip'. Kerry Hannon, USA TODAY, 6/2007.
Image source: Amazon.com.