If someone treats you bad, just remember that there is something wrong with them, not you. Normal people don't go around destroying other people.
There are many reasons why you may start pushing someone away, but if you do this you could end up regretting it when the person leaves for good. You will find many pushing someone away quotes that show this is not a game you should play unless you are sure you no longer want the other person in your life any more. You may decide to start pushing someone away because they are a bad influence and you want to end the relationship. Pushing someone away is a common response if they have hurt or betrayed you in some way. When a significant other cheats the easiest thing to do is to push them away instead of working on the relationship issues that led to the infidelity.