see the forest for the trees
Definition from Wiktionary, the free dictionary
Alternative forms 
- (idiomatic) To discern an overall pattern from a mass of detail; to see the big picture, or the broader, more general situation.
- Smith is good at detail, but can't see the forest for the trees.
Usage notes 
- As demonstrated by the example sentence above, it is used in negative constructions, often starting with can't or couldn't.
to discern overall pattern from details