verb/sə ʃɑ̃.ʒe le i.de/
to start a new activity in order to change one's state of mind, to take a break from doing something boring or to escape from a displeasing situation
“J'en ai marre de cette ambiance tendue ! Je sors pour me changer les idées.” — I'm sick of this tense atmosphere! I'm going out to clear my head.
Literally, “to change one's ideas”