-아/어야지 되다 is the spoken cousin of -아/어야 되다, "have to": 적응해야지 되니까, 그렇게 해야지 돼요, 빨리 김치를 먹어야지 돼!ㅋㅋ. The extra -지 makes it sound more conversational and a shade more insistent, like "you've really got to." Every line here is casual speech, including advice being repeated back from someone else (PT 선생님께서 '한 30번은 해야지, 배워야지 된다). In writing or anything formal, use -아야 되다 or -아야 하다 instead.