It doesn't get much worse than when your ex starts seeing someone else. News of this can hit you like nothing else and completely crush your spirit. Most times, once it happens, the majority of people will give up. But does it really have to be that way? Is there a way to get your ex back even if they're with someone else?
In short, yes; but it may not be as easy as you think.
Once your ex is involved with someone else, your relationship with him/her takes on a whole new dynamic. If you think it was tough getting them back before; you ain't seen nothing yet.
However, if you're still convinced that they're your soul-mate and you are destined to be together, then the effort required to get them back should be inconsequential.
The first thing you want to do when you find out that he/she is seeing someone else is to remain calm. Although your emotions and anxiety will be through the roof, it's important that you control these feelings. If you can't control yourself and you confront your ex or their new partner, you'll be doing irreparable damage.
Next, you'll need to sit down and think about why your ex is with this person. What do they have that you don't? Why did he/she leave you for them?
The next step involves fixing your faults. You should have a pretty good idea of why your ex left you. Although it may not all be your fault, there are things you can do to improve in areas you are lacking.
Next, you want to start living life large. Experience new things and make new friends. Don't be afraid to date and mingle. Your ex must know that you are no longer consumed by grief and you are getting on with your life. You mustn't appear as though you miss them or can't get over the relationship. If you can rise above this, you're going to have much more power and a better chance at getting them back.
Keep in mind that this is a long-term approach and nothing is ever going to happen unless your ex breaks up with their current partner. While it's not 100% certain, taking this approach will put you in a good position to take advantage of any opportunity that comes your way.