Guys... please tell me honestly how stubbornness can affect a relationship/marriage?

It doesn’t work in a marriage

Ehh it can help someone maintain their boundaries and not get caught up in things they don’t want/nerd.

Mostly though in relationships it screws up their ability to work together as a team in a fair way_

It does not as it will build into resentment has been my experience as the person being stubborn is trying to get their way as oppose to what the marriage needs.

In a relationship, there needs to be give and take. Stubborn for the sake of stubborn'ess is a realtionship killer.

[i]"A great relationship is about two things, appreciating the similarities and respecting the differences."[/i]

I refuse to tell you anything about it..

The insistent and persistent belief that you have never been wrong in a single argument. That's the first thing that comes to my mind.