As for what frustrates him most, the worst thing is misunderstandings among friends, either because he messes up something he did for a friend with the best of intentions, or because he feels a friend is not treating him with sincerity.
至於為哪些事常常不爽呢？說穿了，不過是朋友間傳話的誤會啦，一片好心要幫朋友辦事卻辦砸了啦，或是覺得朋友沒有用心對待他等等。