Lizard, I think you do have a point, in that , even for the strongest most well balanced marriages there is most likely SOMETHING that could cause difficulty
The stronger, more well balanced, marriages most likely also have a better handle on those things and have worked out a way of dealing with them before they become a serious factor.
I know that for us something may come up and one will look at the other and we will know what we should do at the time without saying a word.
We know that neither will ever do anything intentionally to hurt the other.
If we get blindsided, the first time, then we get over it learn and move on. We have been together for a little over 40 years. The number of things that can be dealt with by a look, has grown over the years.
That is part of the process of our relationship becoming stronger and more balanced.
Are we invulnerable? Of course not.
Confident enough in ourselves and our limits? Yes.