The Tetris effect (Wikipedia article) is a powerful example of how our brains become habituated based on our focus. Prolonged playing of Tetris can result in seeing real life as a game of Tetris, trying to find the shape to complete a line, seeing Tetris shapes in every day things, or dreaming of Tetris shapes. Studies with brain imaging technology has shown it only takes a few minutes of playing for the brain to become “trained”.
Our brains work the same way with other things we do with them. If we focus on the bad, we see more of the bad (this was mentioned in the article I linked to yesterday). If we look for things our spouse does wrong, we will see more and more things she does wrong. That alone is bad, but even worse is the fact we can’t look for both good and bad at the same time. If we are looking for the bad, we will miss the good. Our focus on the bad results in a skewed view, making her look even worse than she is.
Of course this works in reverse as well – if you focus on seeing the good, some of the bad won’t register, and some of what does won’t seem as bad. You might develop a skew which shows your bride to be better than she actually is. I think that is far better for both of you, and healthier for your marriage. This was the reason for the 3 things for 21 days article I did a couple weeks back. As silly as it seems, it works. When you have to look for three new good things every day for three weeks, your perception changes for the better.