Unfortunately, I have been in both sides. I first had my heart broken when I was 20. Like any normal human being, I cried, ate chocolates, grieved for my heart and moved on.
A couple of years after, I have broken someone else's heart and while I thought having a heart broken was the most painful thing a person can have, breaking a heart apart from yours is as equally sad. I hope I never have to do this again in my life.