Why do ex's do that???

Ok, here's my ques...why is it that ex's try and do whatever they can to get your attention, when they know you've stopped giving it to them and moved on...even AFTER they've dumped you??? I'm in this situation...and I'm confused...it's like damn if you do, and damn if you don't...I gave all the attention in the world to my ex, but now that I've decided to move on, my ex wants to come back, what gives....mind games???