The case of a believer is amazing! Every affair of his is good for him, and this is not for anyone except a believer: if he experiences something pleasant, he is grateful to Allah and that is good for him; and if he comes across some adversity, he is patiently persevering (i.e. has sabr) and that too is good for him!
— [Compiled in Sahih Muslim] (via alilmiyah)