How to move on from someone with whom I am extremely attached?

I was talking to this guy for over a year. And now he became a part of my life, a habit. He told me that he isn't interested in me. Still I keep texting him because of my attachment. I made him centre of my world but he never. He doesn't have any attachment. He can stay without texting me. But I can't, I become so anxious and panicked when I couldn't text him. What should I do?

How to move on from someone with whom I am extremely attached?
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