hi, what is the meaning of "lightbulb went off for me" in this sentence: "As I went on to tell her about the ups and downs, joys and frustrations of parish ministry, a lightbulb went off for me." the speaker is a pastor who gets tired of his job. it seems that he starts to understand something while talking to another person. am i right?

This is a mixed metaphor, but it is intended to mean that the speaker had a sudden realization or recognition. The proper metaphors are an alarm / a warning went off and a light went on.
Also, sometimes in cartoons, when the character gets an idea, it is shown by with a lightbulb over the character's head. I also call them "ah ha moments" - when something becomes clear to you.
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but, why do we say "go off" but not "go on"?
I understand it more as a loss of enthusiasm or of understanding.

The opposites would be 'come on' and 'go off'.

'As she was talking a little light bulb came on in my head and I felt much happier.'

A more literal sentence would be - 'As we approached the house the light over the door came on.'
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I believe that the phrase "a light bulb went off" evolved from "a bomb went off" (meaning that a bomb exploded). The 'correct' phrase should be "a light bulb came on" because a lit light bulb above a person's head symbolizes enlightenment. In animated cartoons such a light bulb goes from being off to suddenly being on. That suddenness could be characterized by an exploding bomb. Thus, combining those two ideas, results in "a light bulb went off."
I've never in my life heard 'a light-bulb went off'.

Always 'a light-bulb went on'.


If a lightbulb goes off, that lighbulb was on previously. Now with the lightbulb off, you are in darkness. Great ideas come with light. This phrase "a lightbulb went off" is a mix of two popular phrases: An alarm went off / A lightbulb went on. You only have to think logically to see how to correct your mistake about how great it is if a lightbulb goes off. This is much easier to correct in your brain than the silly phrase "I could care less."

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