get something out of one's system
1. Lit. to get something like food or medicine out of one's body, usually through natural elimination. He'll be more active once he gets the medicine out of his system. My baby, Mary, ate applesauce and has been crying for three hours. She'll stop when she gets the applesauce out of her system.
2. Fig. to be rid of the desire to do something; to do something that you have been wanting to do so that you aren't bothered by wanting to do it anymore. I bought a new car. I've been wanting to for a long time. I'm glad I finally got that out of my system. I can't get it out of my system! I want to go back to school and earn a degree.
3. Fig. to do so much of something that one does not want or need to do it anymore. I got riding roller coasters out of my system when I was young.