out of one's system

out of one's system (out of one's thoughts or inclinations)

get sth / sb out of one's system (to get rid of a bad feeling or a need to do sth, often by expressing that feeling or by doing enough of sth so that you do not want to do it any more ) — выбросить из головы, перестать думать (о ком-л. или о чём-л.); избавиться от навязчивой идеи, неприятных переживаний, беспокойства; перебеситься (избавиться от навязчивого желания делать что-л.) || ~ плюнуть (и растереть) || выговориться, излить душу; высказать наболевшее

Example 1: Why don't you try and get him out of your system? — Да плюнь ты на него, наконец!

Example 2: You need to get your ex out of your system.

Example 3: I fell out of love with him the first time I found out about the other women. It took me a while to get it all out of my system.

Example 4: There's a lot of anger in her and she has to do something to get it out of her system. (Cambr.)

see also
get over sb/sth
[сome clean]
[get sth off one's chest]
[make a clear breast of it]

This idiom uses system in the sense of "all one's physical and mental functions."