Now that you are over being sad about your breakup, you might want to make your ex regret leaving you. Set yourself up for the road to success in this endeavor by reading on. Once you decide to make them jealous, first ask yourself why you want to do this. If the answer is that you want them to regret it, then this is the right answer. If you want to hurt them in any way, you should reconsider, as hurting someone for your joy is just not right.