Mosquito
The type of insect that ruins your writing is the mosquito. You're trying to write, when you hear that horrible high-pitched mosquito noise in your ear. You jerk your head and swat and it's gone. But when you look down, there's lines all over what you were writing.
Imagine sitting at your desk writing when a mosquito starts bzzzzing in your ear. You can't ignore it, it's gonna bite you. So you flail around helplessly.
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That mosquito noise sounds like it's driving a tiny car (か) in your ear. How are you supposed to write with a bug driving around going bzzz bzzz like a revving car?
You can't. You can't write like this. You need to kill the mosquito and its little car too.