Assalam o alaikum!

The most important thing i want you guys to remember is that you would definitely find many people around you who say, "Yar ye tou tumhari pehli attempt hai...ye sirf experience ke liye hoti hai.agay 2 attempts pari hain tum un pe focus karo." DO NOT EVER LISTEN TO THOSE PEOPLE!
Anyone can clear in the first attempt if he/she studies SMARTLY. CSS is all about managing your time and making the most out of it!
You do not really need to study 16 long hours for the whole year. Keep a balanced approach.
I did study hard but during my preparation I took one month off (I did not plan it though). I was down because I started to think that I might lose focus but after a month or less, I was again on the fast track and studied as I did before the month long break. So the reason behind telling you guys all this is only one and that is you will experience many ups and downs during preparation and in the exams as well. And if you manage to endure all this, You will be victorious!