Preface: There exists a wide array of anecdotes that are the exception to what I'm about to say. If your story is one such where you did manage to make things work after a reconciliation, congratulations. This post is not for you.
When you break someone's heart like a crumpled up piece of paper it's never the same again. You can smooth it out with changed attitudes and behavior, but the wrinkles will still be there, the past hurt will remain ever lingering in the back of thwir mind, even after the most tear-filled reconciliation.
In letting your ex back in you risk letting your heart being broke again worse than before and more damage, especially if you vented to friends and family about your relationship (see also Big Ed & Liz on 90 Day Fiancé). Moreover people don't change for others, but for themselves. A person doesn't recognize a problem till they recognize it fir themselves. Are you really willing to take that chance? I hope not.