not able to see the forest for the trees

not able to see the forest for the trees

Cliché allowing many details of a situation to obscure the situation as a whole. (Not able to is often expressed as can't.) The solution is obvious. You missed it because you can't see the forest for the trees. She suddenly realized that she hadn't been able to see the forest for the trees.
See also: able, forest, not, see, tree