bang (one's) head into a brick wall

bang (one's) head into a brick wall

To attempt continuously and fruitlessly to accomplish some task or achieve some goal that is or seems ultimately hopeless. Some people are never going to agree with you on this, so it's no use banging your head into a brick wall trying to convince them. I feel like I've been banging my head into a brick wall trying to understand this math equation.

See also: bang, brick, head, wall