Let us face it, nobody is perfect, we all have our faults and these lead to relationship conflicts. If the faults are minor and are regarded by the partners with understanding the relationship will just cruise along. However if you view a fault with a magnifying glass, the fault will get bigger and bigger. Continuing focus on faults could get out of hand, the understanding part goes out the window and we have a relationship struggle on our hands.
Eventually there would be a breakup and the parties involved will just blame each other. Very seldom it is the fault of one party, most likely both are at fault to some degree. What you would want to do is to fix your part of the fault and forgive the other part. Forgiveness goes a long way in a relationship. If you would forgive your mate, your mate would likely forgive you in return.
You must believe you can correct your mistakes, eliminate all negative beliefs and built up inner strength and confidence. However you must be able to identify the mistake, which is not easy and is not readily apparent, as you would suppose. In this department you would need expert help.
Having identified the mistakes your task at hand is now to convince your ex that you can change them. You probably would not know how to do it; otherwise you would not have the breakup in the first place. Once again you will need expert help.
Your ex will want to get back with you; nobody wants a breakup if it can be helped. If you ex can see a good relationship ahead reconciliation is easy. Help yourself to see it and help your ex to see it.

