Can't see the wood for the trees

"can't see the wood for the trees"  (British, American & Australian)

if someone can't see the wood for the trees, they are unable to understand what is important in a situation because they are giving too much attention to details.  After you've spent years researching a single topic you get to a point where you can't see the wood for the trees.

Autumn has to be my favourite time of year. The colours, hazy light and cool days are so lovely. I'm not really one for hot weather. You also have to admit dressing for Autumn/Winter is so much more exciting too. Think of the hats, scarves, gloves you can accessorise with!

The boys and I were on a search for conkers today as we've heard that they keep spiders out of the house. (Is this an actual scientific fact?). Unfortunately, we were out of luck as our nearest wood is made up oak, sycamore and birches. Never mind, that didn't stop the boys from enjoying a couple of hours den building practice while the industrious squirrels scampered around us burying their nutty treasures.