There are many people that know because they have probably learned the hard way, that when it comes to winning an old girlfriend back, you have a hard task in front of you, one which is doomed to failure unless you go about it the correct way. There are many websites today that offer advice on how to get your ex girlfriend back and whilst all girls are different and so there can be no guarantees, often their advice is good and offers you the best chance of success.
All these websites are unanimous in stating that you should never begin ex to come back to you as, if you do, the relationship will not last even if she did return and the reasoning behind that is that when you beg, she loses respect for you and you will never be able to regain her respect. Although some sites also suggest you should not grovel, most sites acknowledge that at least some groveling will probably be necessary provided you leave it short of actually begging.
A mistake that many guys make is that they talk to the girl of their past good times when trying to convince her to return but according to the websites, all that does is also remind her of what went wrong in the relationship and why she finally decided to leave you. The sites, therefore, recommend that instead of dwelling on the past, you look to the future and talk to her about what could be if she were to accept you back.
There will obviously, usually at least, be a reason why she dumped you and it is very important, if not essential that you know and fully understand that reason, even if you may not agree with it. Before she takes you back she will want to know that the reason she left you has been addressed or at least is being addressed. You can of course just tell her you will change but it is doubtful that she will just take your word for that so she will have to see steps you have taken to ensure the change or changes are being made. This is not always easy but nothing about getting an ex back usually is. It is for this reason that you should only attempt it if it really is the thing you want to do and are sure that no other girl can take her place.
Of course, if you have decided you want to win an ex back, as she is so special, you will want the relationship to last and so any changes that you make in order to win her back, are probably going to have to be permanent changes. If for instance, the reason was she left you was that you were not romantic enough, you will have to try and remember to do romantic stuff at least once in a while or perhaps lose her again.