Keep your nose clean
Definition 1 of 1
Pro Tip 1/3Avoid Trouble
Focus on choosing actions that won't lead to problems or negative consequences. 
He kept his nose clean by turning down the invitation to the illegal party.
Pro Tip 2/3Good Behaviour
Good behavior means following rules and laws, being respectful, and not causing disturbances. 
She's been keeping her nose clean by volunteering and studying hard.
Pro Tip 3/3Cultural Nuance
This phrase is often used when someone has a history of problems but is trying to live responsibly. 
After his release, he vowed to keep his nose clean.