"What goes around comes around" common english 
phrase referring to the ancient idea/phenomenon 
known in other cultures as 'karmatic retribution' 
or 'The Rule of Three'.  

Basically, it means if you do good deeds, you get 
that positive energy back in your everyday life, 
but if you do bad deeds, that bad energy comes 
back to smack you in the face.  In Buddhism (and 
I'm pretty sure Daoism too), it can come back to 
you in future incarnations or in your current 
life; in more pagan cultures it means you get it 
back here and now, and amplified threefold.  In 
the general goes around comes around sense, it's 
pretty much what it says.  

-_-

-DGR (who just finished courses in both ancient 
chinese myths & legends as well as a course on 
historical vs modern perceptions of witches...and 
both concepts got drilled to death)