I have looked it up in many dictionaries - it is not there Emotion: thinking
I tried to guess the meaning from the context but it seems difficult. Can anyone help?
There are two sentences in the textbook:
"We're just hoping that she'll get it out of her system and then come to her senses and go back to her studies." (parents speaking about their daughter who wants to become a pop singer; they disapprove of her decision)
"If you want to go travelling, it's best to get it out of your system before you start a career. Afterwards it's too late." (an example sentence illustrating the usage of the phrase)

I guess it might mean something like "get this idea out of your head" or "stop thinking about it" but I am not sure...
Hi and welcome to the forums!

Here's the entry at Cambridge online dictionary of idioms :

get it out of your system

to get rid of a bad feeling or a need to do something, often by expressing that feeling or by doing whatever it is that you want to do
If she wants to see the world, it's best that she does it now, while she's young, and gets it out of her system.
There's a lot of anger in me and I have to do something to get it out of my system.

Emotion: wink
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Aha! I should bookmark the Cambridge online dictionary of idioms! Emotion: smile

Thanks for help!
You're welcome!
MissLadybirdI should bookmark the Cambridge online dictionary of idioms!
Definitely, a wise choice.
But I must warn you: you won't find everything there. (Same goes for all the dictionaries of idioms I know Emotion: sad)