Advice to foreign students: do not ask yourself why your fellow students are constantly stressed out and you are not. Use the word, though, but do not take it seriously in the meaning you would give to it in your own language. Advice to local students: diversify your vocabulary when you communicate with foreigners. “Stress” has a dramatic quality you probably do not want to express.
Expressions of laziness and unpreparedness might also be slightly confusing to non-locals, particularly because ambitious students utter them as much as horrible ones. These expressions do not echo a lack of work ethos or professional ambition. It is rather about, about, euh...God knows what it is about.
Anyways, advice to newcomers: be industrious in real life, but lazy in your discourses. Work hard at home, but say you don't. This is not lying – this is integration. The same can be said about “Ich bin total fertig”. Sounds like “rien ne va plus”, right? Sounds like throwing the towel in the ring and changing study programs. Newcomers: try not to be affected by these utterances. Life will go on. Your fellow students will be back next day. Local students: slightly tone down your expressions of frustration regarding your studies. They are alienating.
Find more talking tips here and here.