My dear fellow. Believe me, you have the potential to pass the exam of CSS. How? How did I get to know it? Your desire. Your desire and courage; your dream and most importantly your own words go thus: Based on evaluation from reputable CSS instructors, I have been advised that I can do it. That I understand things analytically and can form an opinion. But then again, with CSS there is no guarantee.
So, you have a dream ahead, Your dream is worth achieving and worth sacrificing. Quit Your job and gird your loins to achieve your dream.
CSS is no doubt a game of luck. But it's also true that luck favours the brave. Remember the words of Paulo Cohelho's "The Alchemist" which goes on thus that If you want to achieve something, the whole universe conspires to help you out.
We are here. Select your optionals. Follow the study plans. Polish your writing skills. Ask whatever you have questions in mind. Study late at night burning the midnight's oil. You will surely get your dream.
One more thing, God forbids, if you are not able to pass this exam at your last attempt, don't be shaky. And you shouldn't feel sorry then for not passing this exam. The reason is that you tried your best to do the best. But you couldn't do so. Feel proud that at last you tried to fetch your dream. Remember, this was the same message that is given by Paulo Cohelho in "The Alchemist".

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"But screw your courage to the sticking place,
And we'll not fail." _Shakespeare, 'Macbeth')