Blot your copybook
Definition 1 of 1
Pro Tip 1/3British Origins
This is a British phrase not commonly used in American English, so it might confuse US speakers. 
When I said he blotted his copybook, my American friend had no idea what I meant.
Pro Tip 2/3Not Literal
The phrase is metaphorical and doesn't involve actual ink or books; it's about reputation. 
After the scandal, the politician had really blotted his copybook.
Pro Tip 3/3Social Context
Mostly used in social or professional contexts where trust and behavior are important. 
She blotted her copybook with the team after lying about the project's progress.