This is a great mantra for those of us who are newly graduated, searching for a new career, or currently unemployed... I have recently come across a few blogs and recent articles discussing the fact that graduates or other young adults are upset by the jobs they are being offered, if they are offered any at all. They think working at a McDonald's is beneath them, even though it's the ONLY thing available.
I hope to never be this way, because you never know when a new opportunity will come knocking on the door while you are working at McDonald's, or at a "crummy" entry level position. Everyone has to start somewhere, and if you do your best at any job, whatever it may be... people notice. They notice your attitude, your hard work and your drive, and it always pays off, not matter how long it takes.
So if you get a job, any job, you should be thankful and try your hardest at it. Eventually the tides will turn, and if you have the right attitude, ideas, and help others out, people will notice and you never know where you might end up.