You don’t. You just do it anyway. Being readily available to an ex who left you isn’t going to make them want you back. Cutting them out of your life won’t guarantee that, either, but it’ll make it hurt far less, and you’ll heal faster, than hanging on to any kind of contact with them will ever allow you.
You can also stop and look at what you said. You don’t want to destroy something that’s already destroyed. It can’t get any worse!