What does Mrs Cooper mean in her two lines?

Sheldon: What do you want, mom?
Mrs Cooper: You know how your daddy used to say that you can only fish for so long before you got to throw a stick of dynamite in the water?
Sheldon: Yeah.
Mrs Cooper: Well, I'm done fishing.

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So did Mrs Cooper stop fishing because Sheldon might throw a stick of dynamite in the water?

By the way, is that some altered version of famous saying?

Can I ask you one more question?
Does the sentence happen to suggest that Sheldon throw a tantrum so easily?

I got it, I think. His mother(Mrs Cooper) may be suggesting by her reference to fishing that Sheldon should go apologising to his boss to get his job back even if it's a drastic way for him to do (apologise).

This is the one with subsequent lines.

Mrs Cooper: You know how your daddy used to say that you can only fish for so long before you got to throw a stick of dynamite in the water?
Sheldon: Yeah.
Mrs Cooper: Well, I'm done fishing. (Throwing a pair of trousers on the bed) You put those on.
Sheldon: What for?
Mrs Cooper: Because you're going to go down to your office, you're going to apologise to your boss, and get your job back.
Sheldon: No.
Mrs Cooper: I'm sorry, did I start that sentence with the words "if it please your highness?"
Sheldon: I'm not going to apologise, I didn't say anything that wasn't true.

Your explanation definitely makes sense. Thanks for answering lots of questions. I can't thank you enough.

This is the one with the preceding linesz

[Sheldon's bedroom]
(He is building a model of some kind of double helix There is a knock on the door)
Mrs Cooper: (entering) Good morning, snicker-doodle*.
Sheldon: Morning.
Mrs Cooper: Oh, well that looks awful fancy, what is that?
Sheldon: It's my idea of what DNA would look like in a silicon based life form.
Mrs Cooper: But intelligently designed by a creator, right?
Sheldon: What do you want, mom?