By Alison O'Brien

Rock Center

It happens in a lot of new relationships. Every day, you learn something new about each other. It happened with David and Kristen Finch.

“David was quirky,” Kristen said. “Always just very sweet and funny, [and] kind of nerdy, but in a cute nerdy way.”

“Very sexy nerd,” David interjected and, smiling, Kristen agreed.

The two met while attending high school in their small Illinois town and after years as friends, David and Kristen began dating. To Kristen, he was “super boyfriend” – a go with the flow guy who was the life of any social gathering.

“He was entertaining the whole room,” said Kristen, age 35. “And it got people laughing.”

But, when they married in 2003, the laughter stopped. Kristen was confused.

“I thought, what happened?” she said. “You know, it was almost like night and day after we got married.”

Once they were living together, David’s actions, once quirky to Kristen now seemed strange. They began to put a strain on their marriage. David, then in his twenties, was obsessed with daily rituals. He would take an hour to make his breakfast. He’d meticulously wash and cut grapes, make his oatmeal and tea. When it came to his eggs, he would line up the carton making it parallel to the countertop and carefully scramble his eggs to make sure the consistency was the same from one day to the next.

WATCH: Kate Snow's full report about Asperger's Syndrome, "The New Normal," from Rock Center with Brian Williams.

David, who was working as an engineer, had an outfit for each season. In the winter, he’d wear a sweatshirt with Eastern printed on it and track pants. In the summer, he’d wear a t-shirt and shorts that became so worn, they developed holes. Every day, he had to wear the same clothes because if he didn’t, David said he “would silently freak out.”

NBC News David Finch staring at rooftops, one of the rituals that helps calm him.

“Tension would mount and I couldn't say anything. Pretty soon I'd start snapping at people,” he explained in an interview with Kate Snow airing Thursday, Sept. 27 at 10pm/9c on NBC's Rock Center with Brian Williams.

The rituals would continue until bedtime. Every night, David would stare out the window at his neighbors’ rooftops. He found the symmetry calming.

“I have a physiological response,” he said. “My shoulders relax. My head calms down and it's kind of nice.”

But it wasn’t so nice for Kristen. While she took care of the house and their two children, daughter Emily and son Parker, David was fixated on himself. When things didn’t go exactly as planned, he’d obsess endlessly. It happened one Thanksgiving when there was garlic in the mashed potatoes. According to David, garlic didn’t belong in the mashed potatoes at Thanksgiving dinner.

“I would sit there and I would complain about it,” David recounted. “And I'd bring it up constantly to Kristen. And then she would get on my case, because she would be very confused. She thinks I look like a baby and I think this is completely unfair, but I don't know how else to react. And so that would set me off.”

In recalling the incident, Kristen said, “I’m thinking how am I going to do this the rest of my life?”

Things were spiraling out of control until March 13, 2008. Kristen, a speech therapist who works with autistic children, was doing research for a client when she came across an online quiz. It was a test of Asperger’s Syndrome, an autism spectrum disorder characterized by repetitive tendencies, obsessive interest in several narrow subjects, difficulty reading the emotions of others and social difficulties. When she started reading the questions, Kristen says, she realized her husband had Asperger’s.

“All of a sudden, the light bulb went off,” she said.

David Finch on Asperger's Diagnosis at 31: It was a 'moment of self-recognition'

She had David take the quiz, but didn’t tell him why or what it was about. The questions ranged from “Do you find it vitally important to remain undisturbed when you’re focusing on your special interests?” to “Do you feel tortured by certain clothes?” The longer the quiz went on, the more personally revealing the questions – and his answers – were.

At the end, the computer tallied his score - 155 out of 200 possible points – and determined it is likely he had Asperger’s. He cried.

“I cried because it was this moment of self-recognition I had never had before,” he said.

A doctor confirmed his diagnosis and, at age 31, David finally had a reason for his behaviors, and an idea of what may be causing his marriage to suffer. In the same way he obsessed over his neighbor’s rooftops, he was now obsessed with fixing himself and his marriage to Kristen. He decided on his own that he needed to modify his behavior.

“I wanted to change,” he said. “I wanted to learn how to manage these behaviors. To give myself a better life, to get our marriage back on track and to earn back Kristen's friendship; to be a better dad and to have a more fulfilling life.”

But David didn’t keep that news to himself. Instead, he decided to go public with his story, writing a memoir which became a New York Times best-seller called “The Journal of Best Practices.”

It’s not a self-help book, but a book about his journey of self-discovery and his efforts to save his marriage to Kristen. It grew from notes he wrote reminding himself to break out of his head and be more responsive to those around him, be a present husband and father, and pay attention to the needs of other people. He even wrote reminders about simple needs such as not to change the radio station when Kristen is singing along, and as important as taking initiative and being a dad.

“I’ve made being a better husband, the husband that I want to be, my special interest,” the 35-year-old David said. “And it’s paying off.”

He’s seeing results in many areas of his life. One note, “parties are supposed to be fun,” reminds David to be good, worthy company at a party. While that may seem like a no-brainer to most, it is a difficult task for David as people with Asperger’s often have a difficult time in social situations. Before his diagnosis, the way David would cope in a group was to mimic the behavior of people who he thought did a great job of fitting in. His favorite role was “the comedian.”

“In order to socialize, I found it was easiest just to get people laughing,” David Finch said. “I would do these ridiculous stunts and jokes, and people loved this.”

But getting people laughing, he found, was exhausting and not entirely fulfilling.

“I would keep that up at like manic, frenetic pace for like an hour, and then I would leave the party,” he said.

So David began studying not just the great humorists, but great communicators. One of his favorite people to study is radio shock jock, Howard Stern.

“Howard’s really an amazingly effective communicator,” he said. “What I’m taking away is his system for engaging his listener.”

By adopting his pacing and voice modulation, and taking cues from his body language, David says he has become better company.

“What I can do is I can give them a couple of minutes of that [humor], and then I can slow it down,” David Finch said. “I can get rid of the shtick and I can really engage in a nice conversation.”

David calls this behavior modification, unlearning old behaviors and learning new ones. He is adamant that he is not curing Asperger’s, nor does he believe one should. He simply says that he wanted to change and has made it a priority. Now, four years after his diagnosis, David says he’s still a work in progress, and Kristen says they met in the middle to put their marriage back on track.

“I guess that was why when we got the diagnosis that I knew that we were going to be ok, because I knew we were both willing to change to make it work,” she said.

Editor’s Note: Click here to watch Kate Snow’s full report, The New Normal, from NBC’s Rock Center with Brian Williams.