I remember Jack Hyles constantly exhorting us to not quit (and also not compromise, but, I digress). Learning when to quit (and compromise) has benefited my life greatly. It turns out that quitting may be one of the best moves you can ever make. If you have the time or inclination, I think you may find this explanation of the benefits of quitting by the Freakonomics economists enlightening and entertaining:
http://freakonomics.com/2014/05/29/the-upside-of-quitting-a-freakonomics-radio-rebroadcast/
http://freakonomics.com/2014/05/29/the-upside-of-quitting-a-freakonomics-radio-rebroadcast/