can't see the forest for the trees
Cannot see, understand, or focus on a situation in its entirety due to being preoccupied with minor details. The way he's obsessing over one doorknob when we're renovating the entire house makes me think that he can't see the forest for the trees.
can't see the forest for the trees
Also, can't see the wood for the trees. Focus only on small details and fail to understand larger plans or principles, as in Alex argues about petty cash and overlooks the budget-he can't see the forest for the trees . This expression was already a proverb in John Heywood's 1546 collection.