Toxic

What I am pondering today: When does a relationship become toxic? When is it broken beyond repair? And why is it impossible to see before it's too late?
I have been in this very relationship. Let me make something clear before I go further....
I am a pain in the ass. No, seriously. I am not the easiest person to deal with at times.
When you meet someone who is SO much like you, it is easy to butt heads. When you put 2 stubborn people together 9 times out of 10 you are going to find a brick wall in the middle. And people like that will break it down however they know how. Usually not in a healthy way. Things get out of control.
I really need to learn to stop lashing out if I feel scared or angry. My mouth can turn a normal argument into a life-changing argument. I know just what to say to cut deeply, and I don't hesitate for a moment if I am angry enough. I am incapable of letting someone walk away until I have the last word. This has been my downfall more than one time.
Is everything that has happened my fault? NO! Absolutely not. Am I blameless? That is a big 'NO' as well.
When things get out of control, it is usually the fault of both. Before I go any further, I would like to come clean as an imperfect human. There are 2 sides to every story, even this one.
Let's just say that I'm a work in progress, and I would like to explore where this character defect comes from. Though the bridge is probably burnt this time, I would like to make sure it doesn't happen again. Though this isn't the first time one of my relationships has devolved like this, I would like to make sure that it's the last.
As always, thanks for listening and God bless!