What are you clinging to right now? The same thoughts about your ex? The hope that things would turn out differently? The text you received that you haven't yet been able to decipher or delete from your phone? Whatever it is, if you're clinging to it, you're being dragged around by it.
It's not easy to loosen your grip. As David Foster Wallace said, "Everything I've ever let go of has claw marks on it." So just start by noticing what you're gripping right now. What thought? What thing? What memory? What conversation? Then, slowly loosen your grip. Then, let it go. Over and over again, as many times as you need.