bang (one's) head against a wall

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

Common Names:

Name	Pronounced	Usage
Prasad	-	Indian, Telugu, Marathi, Hindi, Kannada, Malayalam, Tamil, Odia, Bengali, Nepali
Victor	VIK-tər (English), veek-TOR (French)	English, French, Portuguese, Romanian, Dutch, Swedish, Late Roman
FranČIŠEk	-	Slovene
Ladonna	lə-DAHN-ə	African American
Dinah	['dainə]
Theodore	THEE-ə-dawr	English