If you are all heartbroken and desperate because the man you still care about decided that he doesn't want to be with you anymore, it's truly one of the most painful experiences that a person can possibly go through.
As you are reading articles similar to this, you are probably actively looking for a second chance. I suggest that you take this road only if there was no abuse involved and the relationship was not destructive, but...
...you will know that better.
People are different and relationships are in a way different, but at the same time they are also not really that different... You see, the fundamental building blocks and the psychological aspects of a loving relationship are really the same and it's crucial to get understanding for those before anything else can happen. If you follow the right plan and understand why you are doing things in a certain way, you will be acting from a much better position.
1) Even if your natural impulse tells you to run to your ex and tell him how much you love him, that you will always be there for him or beg him to come back, this is just about the most counter-productive thing you can do. You see, men are made to be scared by needy and desperate people so getting your ex boyfriend back will not be an option, just because he feels sorry for you.
You need to win his respect instead and make him want to come back to you on his own accord and you will achieve that by taking a step back and getting your emotions under control.
2) Taking a break for one month from contacting your ex is the next step in the process and is an equally important one. Getting your ex boyfriend back doesn't come without effort, but the effort you will make here to let him miss you for a while will pay off in your favor. Psychologically this is an important move and will get him intrigued and curious about you.
In the meantime it's critical that you work on yourself and pick yourself up. Stay away from drinking or other damaging behavior. This will not make you more attractive to your ex.
Even if you try really hard, there might occasionally be times when you feel blue and it's not so easy to manage completely on your own. Call up some good friends or family members that will understand you, but make sure you don't contact your ex in a burst of desperation or even any mutual friends you may have. (They will pass information over to him and it will not be ideal for you.)
3) If your ex was the one who left the relationship it means that there was something that bothered him and this something is likely to be connected with you. Be honest with yourself and find out what it was.
You can't go back to the same troubled relationship and you can't fix it without knowing where it's broken. Be prepared to change and don't escape that important step.
After you took a distance for one month and if your ex hasn't contacted you by now, make a plan and call him up to see how he's doing. Don't talk about the relationship or about any kind of problems, but just be easy and positive. Act from the position of strength and good will and get to meet him up for a casual get-together. Test the waters and don't bring up the relationship yet. You can talk about that when the right time comes.
I don't want to say that the full process of getting your ex boyfriend back is covered completely in the 3 steps above, but they are a very good start.