When you are absolutely sure that you don’t have it in you to clear the exam. Once you lose your self belief, then there is no point in continuing.
Try telling yourself that you can clear the Civil Services. Do you sound believable to yourself? If so, leave all other thoughts and continue with it. If there was one thing that I never lost during my three years behind the final list, it was my self belief.
Remember. Some times, all it takes is to hang on for just five more minutes.
All the Best.