can't see the wood for the trees

[can't see the wood for the trees] or [can't see the woods for the trees] or [can't see the forest for the trees] {v. phr.} To be unable to judge or understand the whole because of attention to the parts; criticize small things and not see the value or the aim of the future achievement.

Teachers sometimes notice language errors and do not see the good ideas in a composition; they cannot see the woods for the trees.

The voters defeated a bond issue for the new school because they couldn't see the forest for the trees; they thought of their taxes rather than of their children's education.

We should think of children's growth in character and understanding more than of their little faults and misdeeds; some of us can't see the wood for the trees.