I am learning many new Spanish colloquial expressions as I am reading La Sombra Del Viento by Carlos Ruiz Zafón . Caer en un saco roto is the latest one that I have come across. This expression turns out to be quite useful!😃 

 Today I learned a new Spanish expression while watching Use Your Spanish which is one of my favorite YouTube channels.  That expression is: comerse la cabeza . It means to overthink or to think obsessively about something . According to the website Your Spanish Guide , a similar expression is comerle la cabeza which means to drive another person crazy or to insist on something ad nauseum . So, in a nutshell, comerse la cabeza has to do with situations in which you just can't get something our of your head!