Do yourself a mischief Australia British humorous informal
hurt someone or yourself
If you try to carry that suitcase, you’ll do yourself a mischief.
You'll do yourself a mischief if you're not careful with these scissors.
I would have done myself a mischief if I’d carried on wearing this tight T-shirt.
You'll do yourself a mischief if you don't calm yourself down.
Indicates that something which initially seems bad but harmless can become much worse in the future or lead to a harmful development
Starting of the idiom is a verb, we need to conjugate tense for the verb
To do domething based on your emotions rather than for rational reasons
I can't believe that Tom beat his classmate. He's always the one who let his heart rule his head.