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
If you fall for someone's trick the first time then they are at fault.
Are you going to mess with me again? Fool me once, shame on you; fool me twice, shame on me.