I agree with ojaps post above. People do change. I would never in a million years have guessed that my husband would be capable of leaving us and refusing to pay child support. He is an educated professional. Went to really good schools. Came from supportive family (although I recently found out about some major dysfunctions). He was logical and loyal and dependable. To do this is shocking, and makes me believe that I must be this horrific wife for him to have done this. Obviously to him I was. Many of the posters on here are in similar situations.
But then again there are some situations where there are glaring red flags and in order to not repeat those mistakes it is necessary that we recognize them. I think when a relationship starts out with a lot of drama, it is a warning sign. Both people need to be healed in order to have a healthy relationship.