It's not just for getting environment when we haven't yet prepared for exams but the thing being supposed is the fear that many of the students don't appear just because of fear of failing.
One who has prepared well and thinks that he may succeed but then feels fear of failing must appear to get environmemt even though he fails in his first attempt but i agree when said that one shouldn't appear when he is not prepapred well.

(Sorry for my bad English as i write English following Arabic way of talking because i kept speaking Arabic for years and my English talking way merged with Arabic style )