I'm done with preparation and ready to appear in the forthcoming exams. My preparation is satisfactory, but still i feel that i do not know anything and intermittently i decide to skip this year. What should i do in this regard, keeping in view the fact that CSS exams are a game of nerves and persistence.

Sometimes later becomes never.

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Work Hard In Silence. Let Your Success Make All The Noise.

My Advice for you
Please skip this chance and start preparation for 2016 exam, i also going to appear in 2017. i will study for more than two years

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Success is simple. Do what's right, the right way, at the right time.

what if the same situation remains in the next exam ?

AoA Sikander,

don't be daunted by taking unnecessary pressure. What you are facing is perfectionism, which is a big hurdle in any person's success. But what's worse: it affects the best of the best - the rest really don't care too much about anything. So you must be a serious candidate. Reading this might help:
http://www.exeter.ac.uk/wellbeing/re...perfectionism/

Moreover, His First Flight by Liam O'Flaherty might come in handy. Try to get the message from the story: it's the initiative that counts more than anything!

Thirdly, perhaps what's most important is that you shift your faith from that in yourself to faith in Allaah and hand over your case to him. His decisions are best! The best way to do that is offer 2 Nafil for Istikhara and you'll be guided insha Allaah. Don't look for supernatural signs or omens or dreams, just trust your heart and where ever the circumstances seem to be nudging you.

I don't know why people fear appearing for the first time. At most you'd fail, but that'll add a lot to your experience. I bet a person who has failed 1 attempt is much better informed than someone who has never sit the exam. So it's win/win, whether or not you end up clearing it. My call is, Go for it!