挥之不去招之不来
[huī zhī bù qù zhāo zhī bù lái]
This phrase means something (typically referring to a person or feeling) is both unstoppable ('挥之不去': cannot be driven away) and not summonable ('招之不来': cannot be called upon at will). It may refer to complicated feelings, unresolved emotions or an unforgettable person that comes involuntarily into one's mind.