The Hannah Montana star dated the Jonas Brothers singer when she was just 14, and told Amanda de Cadenet on The Conversation that their break-up affected her deeply.
Cyrus said: "I had my biggest heartbreak was when I was 14. I was in love with this person that I thought was perfect, and so amazing and so when you get your heart broken that's all you see: The rest of my life is ruined because he doesn't love me back.
"He doesn't think I'm pretty, then I'm not pretty. He doesn't think I'm worth his time, I'm not worth anyone's time. That kind of thing."
The LOL actress also divulged that she cried for a month after the pair parted, but that her father Billy Ray Cyrus told her that "this too shall pass" in order to comfort her.
Cyrus added: "So I think just remember that 'this too shall pass' and it's not the end of the world... You got to keep going. It's generic, but it's true. It's a big something to remember."
The 19-year-old is currently dating Hunger Games star Liam Hemsworth, who she considers her "first serious boyfriend".
Watch Miley Cyrus talk about Nick Jonas on The Conversation below: