I just wanted to voice an opinion formulated based on my experience, the experience of others, basic psychology and the opinions of professionals.
There are many reasons why second chances don't work. Primarily it's because you, your significant other or the situation hasn't truly changed. You broke up because something was wrong with the relationship. Your S/O fell out of love with you due to the circumstances or perhaps you changed as a person. Maybe you took them for granted, cheated on them or just flat out tried too hard (clingy, insecure, etc). Maybe your life/career is going nowhere. Maybe the excitement is gone. Maybe one of you cheated (**more on that later). There are a ton of reasons and I can't possibly list them all.
However, the main reasons why second chances rarely work is because your S/O will almost always see you as the person you were when they fell out of love with you. You would have to SERIOUSLY change as a person for them to change their opinion of you. This doesn't happen overnight. In fact, it's rare if it happens at all.
If by some miracle you get a second chance, to your S/O it might initially look like you (or they) have changed but usually within six months old habits and personalities return. Six months is an estimate. Some sooner, some later. We are who we are and it's extremely difficult to change our inner selves.
In desperation for a second chance, we do everything we can to cling on to our Ex. We're so obsessed with getting information about them that we neglect our own need to heal and improve in the process. We need to heal ourselves first (no contact is THE healing tool and should not be broken by you) and get over them before we decide if we want to give it another try. Many have said that after they got over the Ex, they didn't have the same desire to get back with them again for various reasons. Mostly it's because they realize it just wasn't the right fit. That's the key here, it probably wasn't the right fit to begin with.
If I had to guess, the success rate of those getting back together and it working out is about five percent. Pretty crappy odds, wouldn't you agree? Would you quit your job if you knew you had only a five percent chance to find another one? Would you have eye corrective surgery if you knew it only had a five percent chance of success? Would you gamble your savings on a stock tip if you knew it had only a five percent chance of return? Probably not. And so should your train of thought be before you attempt a reconciliation.
Also note, if you are the "dumpee" and you attempt a reconciliation before your S/O is ready, your success rate falls to zero. It's the "dumper" who's feelings have to change, not yours. You are not in control of how they feel about you. They must miss you, realize they made a mistake and earnestly want to work things out. Rare indeed. In the meantime, don't wait around for their feelings to change. Stick with no contact and let it heal you and free them to see the new, improved you in a different light, if ever.
There is a good chance if you stick to No Contact that your Ex will eventually contact you sometime down the road. They almost always do. That's no gurantee of a reconcilliation, but if you are the one initiating contact you're seriously jeapordizing whatever chance you have. Put them out of your mind. Stop worrying about who they are with, if they're having sex and if the new person in their life is better than you (they're not, just different). You have no control over that and it only serves to keep you down longer and delay the healing process.
**Now, if they cheated on you or you cheated on them, that's another story. I truly believe "once a cheater, always a cheater." Why expose yourself to misery? You can't trust them or they can't trust you. It's just extremely difficult for someone who has been cheated on to completely trust the other person. Once that trust is broken, it spills over into every aspect of your life. Are you willing to live night and day for months nay years asking them where they are going, what they are doing and who they are going with? That's no basis for a relationship. No mutual respect and trust. It can not work.
Bottom line: If we spent half the time healing and improving ourselves as we did trying to fix our broken relationship, we'd be a lot better off a lot sooner.
Focus on yourself first. It's not selfish as long as you understand you do have needs and they should be met too. Focus on the areas you need to improve upon (Self Confidence, Clingy-ness, Seeking approval from within, etc). Your Ex sees you in a bad light already and that image is almost impossible to change. However, if you work on your own areas for improvement you will be highly attractive to a new mate.
And think about it. Someone NEW who doesn't have a negative image of you (yet, haha), who loves you for who you are and who wants to spend time with you and be a part of your life.
Now isn't that a much better than someone who is cold, indifferent or just doesn't care about you anymore? You deserve to be happy and odds are you will find it down a new path.
Think about it.