Emotions in one sentence

I would like to be able to boil what I know about emotions down to one sentence.  So I'm going to be attempting that from time to time, until I feel like I've got it right.  My first try is: "Emotions are a system that requires fixing and maintenance to run at optimum performance."  I'm going to leave it at that for now and see if I feel like I need to say anything more specific in my one sentence at a later time.