You love a kid but what happens when he starts crying for something and keep on crying until the time he gets it? You get irritated and then, although you realize that it is wrong, you feel like getting rid of the kid (not permanently obviously). The case with elders is not altogether different. It is quite similar as well. If an adult irritates you by constantly demanding something, you will feel like getting rid of him and permanently (the anger you feel for an adult is much more than you feel for a child because you understand that a child is still innocent but an adult is not). Hence, no matter how much you want your ex back, do not be a cry baby and run after him all the time. Do not irritate him by doing this and most importantly, do not piss him to an extent that it becomes impossible for you to make him love you again.
The question, therefore, is How To Win Your Ex Back? And the answer is telling him that you need him but do that in a very subtle way. What you can do is leave a message for him that says that you still love him and want him back. However, do not cry in those messages and compel him to come back by telling him that you are going to die without him or things like that which can easily be categorized as torturing. The best way to Win Your Ex Boyfriend Back in a relationship with you is to win his heart back rather than torturing him to death.
