Why do I still crave attention from my ex?

you crave attention from your ex, because your ex was a big part of your life once. the attention you got in the past probably made you feel special and happy. it's not hard to let go of people that meant a lot in your life once. your ex made you feel special and the attention that you got isn't similar as the attention you get from your family or friends. if you once loved your ex, the feelings won't fade away just like that. it takes time. anyways craving attention from your ex is totally normal and most people do that too.

Him/Her (I'll just write "her"/"she" for convenience). Her being an ex means you are no longer in a relationship, but that doesn't mean you don't mean a lot to each other. So it would be rather odd if you didn't still crave her attention. The ending of a relationship either by you or her, doesn't mean all feelings just stop that instant, otherwise being heartbroken wouldn't be a thing at all, and most know that it very much is. One of the reasons why you crave their attention might be that you still harbor feelings for them, another might be that they are a person that once loved you. So if you have been close enough to love each other and be in a relationship, then you so many emotional bonds that take time to detach.

You're still attached to her/him. Best way to get over this is to isolate yourself from your ex. Worked for me. But me and my ex never went to same school or same institution, so it was easy to do that for me.

It is absolutely normal to want attention from people we were once so close to. The break up is almost never easy and it takes time to heal before you can move on. The healthiest thing to do is focus your mind on the good memories and see them as a completed stage. Once you accept the fact that the past stays in the past you will be ready to slowly continue moving forward. If by the circumstances you are still in contact with your ex (for example working together) it is a good idea to keep being friendly but not to get too personal. Keeping a distance will help see that person in their new role.