We all know someone that has their mind so made up that no one can change it. Maybe that someone is us. We get so sure of something that we refuse to believe that we could be wrong. Sure, there are things to be sure of. The shirt I'm wearing is blue. That's a fact that can be easily proven.
The dangerous place to be is when we believe so fully in something that can't be proven, but we refuse to open our eyes to other options. This is admittedly a tough topic for me because I consider myself to be a Christian. The strongest argument against Christianity is that it can't be proven with tangible evidence. I'm not saying that argument is right or wrong; I'm just saying that the argument exists (again, a fact that I can prove).
So, what's the point of all of this? The point is this. You can't prove facts by using opinion. Separate the two as much as you can. Most conflict in our life (and our world) has to do with differing opinions. When we focus on the opinions, nothing changes, but when we focus on the facts, progress is made.
Don't be afraid to let your guard down and forget your opinion for awhile. This trait is essential in long-lasting relationships and is a great key in solving past issues. If the relationship is worth it, you'll do it!