It's 2a.m. and my eyes are dry and bugging out.  I'm sitting at my couch for what seems like hours when actuality it's about one hour and twelve minutes.  As I crossed the finished line, I dropped the controller and quietly said under my breath, as not to wake up anyone in my house, "Finally, I'm done."
The game I was playing, for those who are interested, was Forza Motorsport 2 for the Xbox 360.  The game is, in one word, awesome.  Okay, two words, hard.  Like many simulation games or any game for that matter with a career mode you start off on the bottom rung.  You're given just enough scratch to buy a D-Class and a choice of what region of the world to start your career.  In this case I chose Asia because of the cheaper starting cars that have good handling and brake power rather than a powerful car with too much horsepower and poor handling.  The car I started with was a Toyota MR-S which is basically a modified version of an MR-2.
So naturally, you begin career races in the proving grounds where there are little to no restrictions besides what career level you are.  As you win races throughout your career you win credits.  The more credits you earn, the higher your career level gets-it's that simple.  Also you can use your credits gained to tune your car.  And just about any part of your car performance wise is tunable.  Eventually, you will need to become very smart and strategical when it comes to selecting what cars to buy and how to tune them.  Early on I got caught up maxing out every car I owned and being forced to sell some cars to have enough money to buy the cars I really needed.  When you progress to the semi-pro and pro racing categories, you are restricted to what you can and can not race with.  The best thing to do is to press the X button before a race and see what other cars you are going up against and then tune your car just enough to be a few steps better.  If you do it just right, you can grab the pole position and get an early lead. 
So after hours upon hours of racing, tuning, and enduring the exhausting endurance races towards the end of career mode, I'm finished.  I gained a ton of cars and won a ton of credits-all of which I spent trying to buy every single car in the game.  I ended up ranking 1,151st in the world according to the ranking system on Forza Motorsport's community website and a collection of empty Gatorade bottles beside my couch for those hour long endurance races.