Having been party to two long term relationships, has given me plenty of experience in the art of arguing. Unfortunately that experience has shown me that I can't do it very well at all.
The major downfalls for me are that:
1. When an argument breaks out--emotions run high and logic runs low (in my experience anyway) and communication breaks down quickly, therefore giving one the perfect opportunity to express one's self in such a way that whomever is at the opposing side of the argument will not understand the point in the least.
2. When emotions run high and logic runs low (for all involved) the lower functions of the brain kick in. Those being the animal instincts of self preservation, defensive response, and low inhibitions. So when one is trying their damnedest to make one's case, the other party is at the receiving end of some pretty harsh words and thoughts and criticisms.
3. Past hurts push through to current times. Be it from the current relationship or prior baggage, old wounds will be protected the best the arguer can manage. Usually this baggage can cause skewed viewpoint and causes further misunderstanding between competitors. eg. being defensive because of abandonment issues can make an arguer believe that the actions of another person were because of some wish or intention to cause pain even though that person is actually not doing anything of the sort but trying to convey a point and may not be doing so very well because of high emotion and low logic.
It's a vicious cycle.
Arguments in the heat of emotion are the worst part of my human experience. There is no defense against it and there is no winning. There is just hurt, fear, mistrust, and misunderstanding.
When communication breaks down an argument begins. It's the same with countries at war.
It's difficult sometimes to take back the ground that is lost when the misunderstanding is still in place. It's difficult to gain back trust that is lost especially when it's part of a deeper hurt not even related to the disagreement directly.
All that can be done at the end of the day is approach the other in respect and love if you are able. Try to start again. Try and try until it's not worth trying anymore. Even then, try some more.
Only when both sides are calm, honest, and understood can an argument be truly settled.
This may take some time, but in most cases completely worth every effort.