1. 좌절(挫折)하다 = lose heart and stop short of one's goals. Give up owing to an insurmountable obstacle. 2. 낙담(落膽)하다 = be severely disappointed, disheartened. 좌절하다 is more about the course of action (not trying anymore). 낙담하다 only tells of an emotional reaction. * 실패해도, [좌절하지 않는 한] 다시 일어설 수 있다 = Even if you fail, you can rise again [as long as you don't lose heart]. - 실패해도 = 실패하다 + -도(even if something happens) => it gives a negative hypothetical condition. - 좌절하지 않는 한 = 좌절하지 않는다 (not lose heart and stop) + -는 한 (as long as). - -는 한 (related to 한 in 限界) = idiomatic adverbial clause for "as long as (some condition holds"). - 다시 일어설 수 있다 = you can(-ㄹ 수 있다) rise up(일어서다) again(다시) => you can recover and try again. Similar sentences: - 태양이 다시 뜨는 한 우린 전진할 것이다 = We will march on as long as the sun rises again. - 식물은 뿌리째 뽑히지 않는 한 살아난다 = Plants survive as long as they are not pulled out by the root.

좌절하다 has a similar meaning to 낙담하다. It means 'be frustrated / be discouraged'. 실패해도 좌절하지 않는 한 다시 일어설 수 있다. Even if you fail, you can rise again unless you are frustrated. ~하지 않는 한 = unless