Saying 2 words most of us overlook can save your tired relationship

My family often makes fun of me for being overly effusive in restaurants:

Oh, thank you so much for bringing the bread - we really appreciate it! Water? I love water! Thank you for being so kind!

Though no one in my family has ever said it explicitly, I imagine part of the reason they find it so hilarious is that I hardly ever show them so much gratitude.

Not even for oh, say, bringing me into this world and putting a roof over my head for 18 years.

So I had a quiet "aha!" moment while reading Janice Kaplan's "The Gratitude Diaries," in which she chronicles her yearlong effort to show more appreciation in different areas of her life.

Before writing "The Gratitude Diaries," Kaplan, a journalist who was formerly the editor of Parade magazine, helped conduct a survey on Americans' gratitude habits.

Results showed that 97% of respondents said they would express gratitude to a server in a nice restaurant (guilty as charged). But how many women said they regularly thanked their husbands? Just 48%.

In the book, Kaplan writes that she gets it - we have way higher expectations for our partners than we do for waiters. Beyond that, she suspects we also get so used to our partner being there for us that we generally forget to appreciate it.

Simply making the effort to say "thank you" can breathe new life into a tired relationship.

When she visited the Business Insider offices in August, Kaplan told us:

"When you're in a relationship, particularly for a long time, you kind of stop noticing somebody. Psychologists call it habituation."

"You get used to somebody. You stop realizing why you wanted to be there in the first place."

During the first month of her gratitude experiment, Kaplan focused on appreciating her husband.

She'd thank him for driving them home from a party or fixing a leaky faucet - and he'd be confused, because he always does those things.

"I know you do," Kaplan would tell him. "But I appreciate it."

As Business Insider's Erin Brodwin has reported, psychologists have known for a while that couples who express gratitude toward each other are more likely to stay together. In fact, thanking your partner even once can bring you two closer months later.

That's possibly because a single act of gratitude sparks a cycle of gratitude and generosity: You thank your partner, so your partner feels appreciated and invests more in the relationship, which in turn makes you feel more grateful to them.

Perhaps the part of "The Gratitude Diaries" that struck me most was a scene Kaplan describes in which her husband, a doctor, is rushing off in the middle of the night to treat a sick patient.

Typically, Kaplan writes, she'd be frustrated and angry that her husband was leaving at that hour. But during her gratitude experiment, she pushed herself to find the reason to be grateful.

So she told him:

"I was just thinking about how lucky your patient is to have you. She must feel so much better knowing you're on the way. The world needs more doctors like you. Thank you for being so special."

To me, this scene reflects how showing gratitude to the people we're closest to can take more effort than thanking the barista at Starbucks. It requires seeing the person in a new light - or simply seeing them at all.

But that effort can pay big dividends. Kaplan writes that her small acts of gratitude appeared to change her overall marriage for the better.

In the book she mentions one professor of marriage and family therapy who told her that every day he emails his wife thanking her for something. It doesn't have to be anything huge - thanking her for running errands when he was busy is fine.

The point is to make gratitude a habit so that, eventually, you don't have to think about it - it's just the default lens through which you see your partner's everyday behaviors.