Ann always thought her parents had a great marriage. When she was growing up they always seemed to get along, they made time for couple-dates, they were great parents. In her marriage she has tried to continue their tradition and replicate as much as possible their relationship.
Bill was all too aware of the problems in his parents' marriage. His father drank too much, had a temper; his mother was perpetually unassertive and passive. He knew exactly what mistakes he needed to avoid. He didn't drink, tried always to be reasonable, and appreciated his wife's sense of spunk and ability to speak up.
We always walk out of our childhoods with some impressions of our parents' marriage, but these impressions are usually black and white, one-dimensional images - their relationship was good and I want to recreate it, or my parents' marriage was awful in these ways, and I'm going to not do all the things they did that seem to get them into trouble. Sounds good. But either path you choose is likely to run you into trouble.
If, like Ann, you decide that you want to try and do what your parents did, and set out to replicate their relationship, you may find over time that you are not quite as happy as they seemed. There is a certain tension that lingers; you have days when what you do and how you feel don't match up.
If, like Bill, you try to steer clear of all the pitfalls your parents fell into, the danger is that you swing too far in the other direction - you don't drink, but in many ways you are a dry drunk; you manage to control your anger, but you internalize and have migraine headaches or find yourself constantly biting your tongue. Your spouse's spunkiness, once appreciated, is now getting irritating and there are times you feel resentful.
While your intentions are good and understandable, the problem for Ann and Bill, and you, is that they are based on limited and hence distorted impressions of your parents' marriage. They are "little-kid" impressions of childhood and adolescence. Ann, for example, didn't know that her father was having an affair for several years when she was in middle school, or that her mother had had a miscarriage the year before she was born and was massively depressed the first couple of years of Ann's life, or that her parents had wild, out-of-control fights when she went away for sleep-overs or to camp. Her kid impressions did not fit the complete reality of their relationship.
Similarly, Bill saw the drinking or the anger or his mother's passivity, but didn't, and couldn't understand how it all was a bad solution to other problems beneath that he was totally unaware of - the fact, for example, that his dad struggled with depression or stress from his job, or that his mother had been abused as a child and was constantly fearful and hypervigilant. Bill and Ann's impressions are too simple. They lack the complexity of an adult perspective. And because they do, these blind-spots create the emotional undertow that Ann and Bill don't understand, but now feel.
What to do? One good start would be for each of them (and you) to have an adult conversation with their / your parents about your parents' marriages during your childhood. Start by asking the easy questions at some intimate time - "Tell what your relationship with mom was like when I was growing up" - and move to harder questions if necessary - "Sometimes I feel angry and stressed for no apparent reason; did you ever feel that way?" Or "Looking back on it, why do you think you drank so much when I was growing up? Is there something you were dealing with?" Or, "I'm just wondering...did you ever think of getting divorced when I was growing up?" The aim here is to not interrogate or blame your parents, but to be curious. You are trying to better understand what made your parents tick, to fill out the picture, so you can better understand what makes you tick. Think of this as upgrading of your psychological software.
If this conversation isn't possible (because they won't talk, because they have passed away) try spending some time reflecting on your parents' lives or consider a few sessions of therapy to help sort this out. The goal here isn't to find The Answer, but rather to make that childhood picture more complex and multi-dimensional.
Like the 3 Pigs, your goal is to hopefully build your relationship on the solid bricks of adult reality, rather than childhood ones of straw.