Just have faith in your abilities and always remember that Almighty is going to have best plans for you .Just try your best and leave the rest up to HIM .
When it comes to preparation every one has different mind set and stamina so it varies from individual to individual .There are many officers who qualified CSS with a full time job as it is about time management and handling the pressure better .

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Logon Ki Zaroraton Ka Tum Se Wabasta Hona Tum Per ALLAH Ki Enyat Hai.