Because the smarter you are, the more you're aware of how little you really know. One of life's most important lessons is to take a moment before you speak, because what is very true for a lot of people is that the smarter you get the less you speak.
Never go back! And if what broke you tries reaching out to you again, ignore them. A valuable lesson for everyone to know. If they broke you to begin with then he didn't love to fight and be better for both of you.