1. make a conscious effort to improve one's work or behaviour
pull up your socks or you will fail
The idiom to 'pull up your socks' is used as a warning to give advice to someone to encourage them to make a greater effort or to improve their behaviour or performance. if you tell someone they should 'pull up their socks' it usually means that their performance hasn't been good and you need them to improve or there could be consequences. This is a popular idiom often used in social and professional contexts, however, it is quite an informal expression, so it might be inappropriate to use it in a formal situation.