"A light bulb goes off in my head" nghĩa là gì?

I wish when a light bulb goes off in my head it would let me know if it's a good idea or not.

As the elevator reaches the ground floor, a light bulb goes off in my head, and I say to myself, "Kids are smarter and wiser, way more than kids raised in the 90s or even before that, all thanks to technology".

There are some sporadic (rời rạc) moments where a light bulb goes off in my head, and I write it down but never get around to carrying it out, in part because I’ll just put it off to the point where I don’t even care to write about it anymore.